The fight for control of both chambers of Congress comes to a head this fall. Shutterstock
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Whether Republicans control both chambers of Congress during President Barack Obama’s final two years in office squarely depends on a handful of U.S. Senate races now entering their final phase.

So far in all Senate races, candidates, parties and other political power players have aired more than 428,000 television advertisements, including both primary and general election-focused ads, according to a Center for Public Integrity analysis of data provided by Kantar Media/CMAG, a media tracking service.

Together, the ads are worth an estimated $153 million — a figure that will only continue to balloon between now and the Nov. 4 election.

Candidates themselves are responsible for only about half of these ads. Nominally independent groups — such as super PACs and politically active nonprofits — are responsible for most of the rest.

While partisan primaries in part account for the messaging barrage, candidates and other political groups have aggressively pivoted toward the general election during summer months — traditionally a period of political calm before the post-Labor Day sprint toward Election Day.

To oust Democrats from power, the GOP must pick up six Senate seats in November.

Competitive races are under way in more than a dozen states, with the battlefield stretching from Alaska to Colorado to North Carolina.

Democratic candidates and their allies have aired more TV ads to date than their GOP rivals in Alaska, Arkansas, Colorado, Louisiana and North Carolina, according to data provided by Kantar Media/CMAG.

Republican candidates and their allies, meanwhile, have bankrolled more ads in Georgia, Iowa, Kentucky, Michigan and Montana.

Thanks to retirements of Democratic lawmakers in Montana, West Virginia and South Dakota, the GOP looks poised to pick up at least three seats.

Meanwhile, Democratic incumbents in Alaska, Arkansas, Colorado, Louisiana and North Carolina are bracing themselves against strong Republican challengers.

And hotly contested open seat races are also underway in Iowa and Michigan, where long-serving Democratic senators have also announced plans to retire.

Republicans are mostly playing offense, except in a few states — most notably, Georgia and Kentucky — where Democratic candidates are mounting well-financed bids.

Both Democrats and Republicans have big-money allies on their sides.

Among the five most active non-candidate spenders so far this cycle, three lean Republican and two are aligned with the Democrats.

The top-spending groups to aid Republicans have been Americans for Prosperity, the politically active nonprofit backed by conservative billionaires Charles and David Koch; Crossroads GPS, a nonprofit co-founded by GOP strategist Karl Rove; and the U.S. Chamber of Commerce, a nonprofit trade association.

On the left, the TV ad wars have been dominated by Senate Majority PAC, a super PAC, and Patriot Majority USA, a nonprofit led by a longtime ally of Senate Majority Leader Harry Reid, D-Nev.

So-called “dark money” abounds: Of these five groups, only the Senate Majority PAC must regularly disclose its donors to the Federal Election Commission. The rest must only reveal information about their funders if money is received for a particular ad campaign — something that rarely happens.

Remarkably, about two-thirds of these 428,000-plus ads have aired in just nine battleground states that will likely determine which party will control the upper chamber of Congress during the final two years of Obama’s presidency.

1) North Carolina

Democratic Sen. Kay Hagan is running for re-election against Republican state House Speaker Thom Tillis in North Carolina, where voters have not re-elected a Democratic senator since the 1960s.

Super PACs and politically active nonprofits have dominated the airwaves in North Carolina, with all non-candidate, non-party groups responsible for about 80 percent of the more than 40,700 ads that have aired, according to a Center for Public Integrity analysis of data from Kantar Media/CMAG.

Hagan’s campaign has repeatedly blasted the Koch brothers, who support conservative nonprofit Americans for Prosperity, for their involvement in the race.

But the top sponsor of ads in this contest? It’s Senate Majority PAC, a Democratic super PAC, which has produced more than 9,500 ads in the race.

That’s about 63 percent more ads than Americans for Prosperity, which has pummeled Hagan for her ties to Obama and her vote for the president’s health care law. Americans for Prosperity’s ads don’t overtly call for Hagan’s defeat, thereby allowing the group to avoid telling federal election regulators how much money its pumping into its messaging machine.

Kantar Media/CMAG estimates that Americans for Prosperity has spent at least $1.8 million on TV ads in the Tar Heel State. Other sources, in attempting to calculate the cost of TV ad buys, have put this figure much higher.

To compete in this environment, both candidates’ campaigns have raised millions. Hagan had raised nearly $17 million for her re-election campaign as of June 30, versus Tillis’ $4.8 million. Hagan ended June with about $8.7 million in the bank, while Tillis reported $1.5 million cash on hand.

Candidates, parties and other politically active groups have, through late August, spent about $2.66 per eligible voter on TV ads.

2) Arkansas

Incumbent Democratic Sen. Mark Pryor is fighting for a third term in a state shaded red — Mitt Romney won 60 percent of the vote in 2012. Six years ago, Republicans didn’t even field a challenger to Pryor, whose family is an institution in Arkansas politics. This election cycle, Pryor is being challenged by freshman Rep. Tom Cotton, an attorney who’s a veteran of the U.S. wars in Iraq and Afghanistan.

Both Pryor and Cotton have been prolific fundraisers.

Pryor raised nearly $9 million as of June 30, and he ended the month with about $4.1 million cash on hand. Cotton, meanwhile, raised about $7.1 million. He ended June with about $2.8 million in the bank.

Notably, through late August, Pryor’s campaign had aired more ads than any other group or the Cotton campaign, at about 5,600. The Koch-supported Americans for Prosperity ranked as the second-most frequent ad sponsor, at about 4,000, according to Kantar Media/CMAG.

In all, non-candidate, non-party groups have accounted for about 62 percent of the more than 31,300 ads that have aired in Arkansas, according to a Center for Public Integrity analysis of data from Kantar Media/CMAG.

3) Louisiana

Incumbent Democratic Sen. Mary Landrieu is facing a tough race for a fourth term, but Louisiana’s election rules don’t pit her against just one Republican opponent. In November, all U.S. Senate candidates run in a “jungle primary,” and if no one candidate secures 50 percent of the vote, then the top two vote-getters will face each other in a December runoff.

Republican Rep. Bill Cassidy is widely viewed as Landrieu’s main challenger, although retired Air Force Col. Rob Maness, another Republican, is also drawing some support from conservative voters.

Landrieu’s campaign had aired more than 13,700 TV ads as of late August, according to Kantar Media/CMAG. That represented about 40 percent of all 34,200 ads in the Senate race.

Non-candidate, non-party groups account for nearly half of all ads aired in Louisiana, with Americans for Prosperity earning the No. 1 spot, at about 4,900 ads.

As of Aug. 2, Landrieu had far outraised Cassidy: $14 million to $8.6 million. However, the Republican challenger reported slightly more cash on hand: $5.6 million versus $5.5 million.

4) Alaska

You wouldn’t necessarily know it by watching the TV ads, but Senate Majority PAC has been a major player in Alaska’s U.S. Senate race. It has provided the bulk of the funds for another super PAC, called Put Alaska First, which supports incumbent Democratic Sen. Mark Begich.

Put Alaska First has aired about 6,400 TV ads, as of late August, according to Kantar Media/CMAG. That amounts to roughly one out of every five aired in the race. In all, non-candidate, non-party groups account for about 52 percent of the more than 33,400 ads aired in Alaska.

Meanwhile, Begich’s own campaign has aired more than 10,100 ads — about 30 percent of all ads.

Begich has also maintained a fundraising advantage over his Republican rival, Dan Sullivan, the state’s former attorney general and commissioner of the Department of Natural Resources.

As of July 30, Begich had raised about $8.4 million compared to Sullivan’s $4.1 million. The Democratic incumbent reported about $2.1 million cash on hand, at that time, while Sullivan reported about $990,000.

Through late August, no other Senate race has a higher rate of TV ad spending per eligible voter — an estimated $6.

5) Kentucky

No matter that Kentucky is a fairly rural state with only a few sizable media markets. Through late August, candidates and outside groups have aired about 37,500 TV ads in this monster Senate battle — with 70 percent from Republican candidates and GOP-aligned groups, including ads run during Senate Minority Leader Mitch McConnell’s primary against tea party challenger Matt Bevin.

McConnell would almost certainly become Senate Majority Leader if Republicans gain six Senate seats after the midterm elections, but he’s under withering attacks from Democrats, particularly his Democratic opponent, Secretary of State Alison Lundergan Grimes.

Grimes has already raised millions of dollars and received endorsements from the likes of Bill Clinton, though McConnell has an even bigger war chest — his $9.8 million in the bank as of late June compares to $6.2 million for Grimes.

Meanwhile, candidate-specific outside groups exist to support both McConnell and Grimes, and the pro-McConnell Kentucky Opportunity Coalition, a nonprofit, leads all others in total ads with more than 9,300. Other big groups — including the American Chemistry Council, U.S. Chamber of Commerce, Senate Majority PAC and Patriot Majority USA — have also been active in the contest.

The estimated spending through late August on TV ads from all sources per eligible voter is $3.64.

6) Michigan

The open seat Senate race in Michigan pits Democratic Rep. Gary Peters against former Secretary of State Terri Lynn Land, who has already pumped millions of dollars of her own money into her campaign. The Democratic-leaning state has already seen a deluge of ads from Koch-connected groups, including Americans for Prosperity and the Freedom Partners Chamber of Commerce.

Team Peters has fought back under the auspices of the Senate Majority PAC, as well as labor unions such as the American Federation of State, County and Municipal Employees and Service Employees International Union. A super PAC supporting Land — founded by retired businessman Paul Mitchell — has also entered the fray, as has a nonprofit called the American Sustainable Business Council Action Fund, which has praised Peters in ads for supporting the auto industry bailout.

Through late August, Michiganders have already watched more than 23,500 TV ads about this Senate race.

As of mid-July, Land’s campaign had raised $8.7 million, while Peters’ campaign had raised about $7 million.

7) Colorado

This race went from quiet to animated when Republican Rep. Cory Gardner announced in March that he would challenge incumbent Democratic Sen. Mark Udall, who was first elected in 2008. Recently, Colorado has leaned Democratic — Obama carried it in both 2008 and 2012. But Democratic state leaders have also recently faced ire from voters over a push for stricter gun control laws and education funding.

Already, conservative groups such as Americans for Prosperity and Crossroads GPS, a nonprofit co-founded by GOP strategist Karl Rove, have been working to lower Udall’s favorability rating, criticizing him for backing Obamacare, for instance. The U.S. Chamber of Commerce, meanwhile, has spent more than $1 million brightening Gardner’s image, according to FEC filings. Udall has been boosted by groups such as Senate Majority PAC, which FEC records show has invested more than $2.6 million into the race through late August, and the League of Conservation Voters.

At the end of June, Udall’s campaign committee enjoyed a $5.7 million-to-$3.4 million cash-on-hand advantage over Gardner.

8) Georgia

This open seat Senate race — incumbent GOP Sen. Saxby Chambliss is retiring — could be one of the nation’s closest, pitting two extremely well-funded candidates against one another.

The Democratic Party has rallied behind Michelle Nunn, CEO of the Points of Light Foundation and daughter of former Sen. Sam Nunn. Nunn has raised more than $9.2 million and still had $4.8 million in the bank as of late June.

Republicans, meanwhile, nominated self-funding businessman David Perdue over Rep. Jack Kingston in a July runoff vote. The primary is a major reason why more than 36,100 ads have already been aired in the race — Republican candidates and GOP-aligned groups account for about 78 percent of them.

Nunn’s own campaign, however, has aired more ads than Perdue’s campaign, which reported about $780,000 in the bank as of July 2.

Special note: if no candidate wins 50 percent of the vote in November — Libertarian Amanda Swafford could complicate matters if the vote is extremely close — the top two candidates have a runoff in January.

9) Iowa

Democratic Rep. Bruce Braley is running against Republican state Sen. Joni Ernst in this open seat race, where incumbent Democratic Sen. Tom Harkin is retiring. Ernst succeeded in uniting several factions of the GOP during the primary, and she gained nation attention for promising to make Washington “squeal” in one notable campaign ad that touted her background castrating hogs among her credentials for knowing how to “cut pork” in Congress.

About 31,500 ads from candidates, parties and other politically active groups have run so far in this Senate race, according to Kantar Media/CMAG, with conservatives accounting for 56 percent of them.

The top non-candidate spender in the race? The Concerned Veterans of America, a veterans-oriented group that is part of the Koch brothers’ political network, which has aired about 3,300 ads.

But as of late June, it was Braley’s campaign that had stockpiled more cash. The Democrat had raised $7.1 million and reported $2.7 million in the bank, while Ernst had raised $2.5 million, with $1.1 million cash on hand.

Best of the rest:

New Hampshire

Freshman Democratic Sen. Jeanne Shaheen will likely face former GOP Sen. Scott Brown, who briefly represented Massachusetts and has now gone north to the Granite State in a bid to reclaim his political fortune. He lost his office in 2012 to Democrat Elizabeth Warren.

Although Brown is expected to the Republican Party’s nominee next week, he nevertheless faces a pair of plucky challengers in one of the calendar’s latest primaries: New Hampshire’s former two-term U.S. Sen. Bob Smith and former state Sen. Jim Rubens, who’s so far received about $1.2 million in support from Mayday PAC, according to FEC filings. Mayday PAC is an anti-super PAC super PAC founded by Harvard Law School professor Lawrence Lessig.


Among all the issues that could affect a Senate race — the economy, energy, military conflicts — plagiarism isn’t typically among them. Except, that is, in Montana, where interim Democratic Sen. John Walsh quit the race in August amid accusations he lifted other people’s work in writing his master’s degree thesis.

Now, Amanda Curtis — a high school math teacher and Montana state representative with meager political resources — stands as Democrats’ emergency replacement against Republican Steve Daines. The Republican congressman’s campaign has already aired more than 10,100 ads in his bid to be the Silver State’s next senator. That’s nearly half of the 21,100 ads in the entire race.

So far, Curtis has received little outside support for what’s now an implausible bid to keep this Senate seat blue.

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Michael Beckel reported for the Center for Public Integrity from 2012 to 2017.