At that Republican retreat in January 2009, gathering inside a historic inn in Annapolis, Md., the group — led by Representatives John A. Boehner of Ohio, the Republican leader, and Eric Cantor of Virginia, the whip — did not tolerate the hand-wringing that consumed so many Republicans that dark winter.

Instead, they walked through a by-the-numbers picture of Democratic vulnerability that had been lost in the excitement over Mr. Obama’s election. Some 83 Democrats held seats in districts that once supported President George W. Bush; more than two dozen won their last elections by wafer-thin margins, according to a Republican document provided to The New York Times.

In their quest to reach a majority, the Republican leaders imposed tough party discipline, warning incumbents that the party would no longer act as a “welfare state” for those who were lax fund-raisers. They began an aggressive recruiting effort for top-flight candidates in districts that seemed to be virtually owned by some of the longest-serving Democrats in the House. And they were keenly aware of the anti-establishment mood, rarely engaging with Tea Party challengers, as Senate leaders did, fearful that any efforts to influence primary races could backfire.