But Democrats argue Blumenthals lead is much larger, and the DSCC released an internal poll this week that showed Blumenthal up 15 points.
Still, McMahons personal wealth has allowed her to run TV ads and introduce herself to voters, and it will let the NRSC allocate its finite resources elsewhere, said Quinnipiac University polling director Douglas Schwartz.
The seat was considered a safe seat for Democrats when Blumenthal got in, but Republicans have to be pretty happy because now its a competitive race, he said.
Similar to Connecticut, Republicans have a candidate who can self-fund in Wisconsin, where Republican Ron Johnson is challenging Democratic Sen. Russ Feingold. The NRSC has so far reserved $500,000 worth of TV time in the state.
Along with Missouri, Democrats are already on the air in Pennsylvania and Colorado, two states in which the NRSC has reserved time in October.
Former Sen. Scott Brown, R-Mass., candidate for U.S. Senate in New Hampshire, holds his hand over his heart during the singing of the national anthem as he waits to take the stage for his town hall campaign rally with Sen. John McCain at the Pinkerton Academy in Derry, N.H., on Monday, Aug. 18, 2014.