Even with the improved environment this year, the party’s chances are still roughly 50-50, according to several election handicappers. And there is concern that contentious primaries — in states such as Georgia, Iowa, Alaska and North Carolina — will again yield nominees who can’t win a general election.

“While the mood has changed, we still have significant work to bring that about,” said NRSC Chairman Jerry Moran, a senator from Kansas.

“We could still blow it and end up hurting ourselves in some way,” added Collins. “But after last year — a rough fundraising environment, the shutdown and disagreements on the right — now people from all sides are starting to come around. … We’ve just got to go out and earn it.”

Democrats say Republican candidates haven’t put up the kind of eye-popping fundraising numbers that back up the rhetoric about a party on the march. They also caution that the election landscape is too unsettled to forecast big GOP gains; it remains to be seen whether Republican candidates in key battlegrounds such as Arkansas, Louisiana and North Carolina have what it takes to unseat incumbents.