These nine Senate races have seen $72 million worth of independent expenditures thus far. As a point of comparison, in the 2010 midterms, nonparty outside spending reached only $97 million — and that was for the whole election in all 37 Senate races. The highest levels of independent expenditures in our sample were seen in North Carolina, with $14 million, and Kentucky, with $12 million. The competitive Senate races also reveal a potential new trend — organizations that benefit a single candidate and hide their donors. These single-candidate, dark-money groups make it impossible to know whether candidate contributors are attempting to curry favor by also making large donations to candidate-specific spenders.
Source: Election Spending 2014: Nine Toss-Up Senate Races | Brennan Center for Justice
