Democrats have plenty of money to press their advantage; the party’s House campaign arm has been crushing fund-raising records, and the most vulnerable Democrats are flush with cash to wage their re-election battles.

But those are not the only reasons that some Republicans are concluding it is not worth even trying. A toxic environment for Republicans in the House, where partisanship reigns and they are judged as much for their segments on Fox News as any policy effort, has taken a toll on lawmakers who are interested in pursuing legislative compromises.

“As the party reshapes itself, there are some members who aren’t as comfortable there as they were when they first came,” said former Representative Tom Davis, Republican of Virginia, who chaired the party’s congressional campaign arm from 1999 to 2003. “Especially for some of these members who buck the party on occasion, they are finding it a less hospitable place to be.”