Would Trump doom Toomey, Pa. GOP?

Donald Trump has already left his mark on the 2016 presidential primaries even before the first vote has been cast. But will it be good for Republican senators up for re-election in competitive states?

Freshman Sen. Pat Toomey, R-Penn., is already one of the most endangered GOP incumbents running next year. His race — possibly a rematch against 2010 Democratic opponent Joe Sestak or else a contest with Kate McGinty, former chief of staff to the state's governor — will help determine whether Republicans hold the Senate. Many local Republicans think Trump makes Toomey's job harder.

"I think that the best chance that Toomey has to carry the state is with either [Marco] Rubio, [Chris] Christie or [Jeb] Bush as head of ticket," said Bob Asher, a Republican national committeeman from Montgomery County. "I think [Toomey] would be seriously hindered if either Trump or [Ted] Cruz were at the top of the ticket."