Republicans worry that Mr. Trumps difficulties in New Hampshire and Pennsylvania, where Republican incumbents are caught between their own base and moderate voters appalled by the partys nominee, could hand Democrats those decisive seats. Senator Kelly Ayotte, the Republican up for re-election in New Hampshire, demonstrated the vise she is in this week when she said at a debate that Mr. Trump would represent a good role model for children, only to recant a few hours later.
Sensing new opportunity, Democrats intend to redouble their efforts to tie Republican candidates to Mr. Trump in states and districts with large numbers of college-educated voters and minorities.
I think its quite effective in New Hampshire, in suburban Philadelphia and in Nevada, said Senator Chuck Schumer, a New York Democrat.
Compounding their difficulties, Republicans are also fending off a challenge to Senator Richard M. Burr in North Carolina, a state Mrs. Clinton is determined to win, and have also become just as worried about Senator Roy Blunts prospects in Missouri. Strategists in both parties who have seen internal polling say Mr. Blunt, whose seat initially seemed safe, is now trailing his Democratic challenger, Jason Kander, a deft campaigner who has been helped by Mrs. Clintons narrowing deficit in the state.