The Center obtained its campaign contribution data from the Federal Election Commission’s website on Dec. 8, 2010, six days after the post-election quarterly deadline.
The analysis included only PAC contributions given to candidates without affiliation to those specific PACs, excluding all independent expenditures, in-kind contributions, and communication costs. The Center’s analysis also excluded PACs that did not give at least $100,000 over both cycles. Finally, any contributions to a candidate from a particular PAC where the total amount given to that candidate over both cycles was negative were excluded from those PACs’ totals. There are various reasons candidates return money to PACS, which show up as negative amounts in the FEC’s campaign contribution data. The Center also used Congressional Quarterly’s MoneyLine for information about specific contributions to candidates from the top 50 PACs. Those data were accessed in January 2011.
The top 50 committees were chosen by calculating the total percentage shift away from Democrats and toward Republicans between the 2007-2008 and 2009-2010 election cycles. The Center also calculated the total contributions to Republicans by the financial and healthcare sectors for each month of the 2009-2010 cycle.