The boost came during a period where his prospects brightened considerably — longtime Sen. Dick Lugar (R-Ind.) lost his primary to Indiana state Treasurer Richard Mourdock (R), a Tea Party favorite who spent heavily to win the race and started off the general election with little money in the bank.

Mourdock has yet to release his fundraising totals for the quarter.

While the state leans Republican, Donnelly has cultivated a centrist voting record and Mourdock has taken some stridently conservative stances Democrats hope will hurt him in the fall. The Hill rates the race a "toss-up."