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The Center analyzed independent expenditure data obtained by the National Institute on Money in State Politics (NIMSP) for 29 states. The Center augmented NIMSP’s data by identifying independent spending in nine other states, primarily through additional government records. The remaining 12 states were not analyzed either because they had no state-level races or they had disclosure laws that were so poor it would make a comprehensive analysis impossible. In states such as Florida, for example, reports filed by committees do not identify the targets of independent spending.

The Center then obtained donor information for all groups with reported spending above $100,000 — which encompassed more than 90 percent of all spending — to determine whether the majority of each group’s funding came primarily from out-of-state donors and whether national political groups, such as the Republican Governors Association or Democratic Governors Association, were among the donors.

Groups were classified as in-state or out-of-state based on where the majority of their donors resided. Additionally, when applicable, groups were classified based on the financial or ideological motives of their donors.

Finally, the Center used data from NIMSP, state filings and news reports to determine whether the $100,000-spending groups supported predominantly Republican or Democratic candidates (or a combination). All spending by state and local political parties was also classified as pro-Republican or pro-Democrat to determine overall spending in support of candidates from each party.

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