WASHINGTON — U.S. House Republicans said an election loss in Mississippi Tuesday may portend widespread voter rejection in the November races, and some complained that party leaders are failing to provide an adequate election-year strategy and agenda.

At a closed-door weekly meeting of House Republicans yesterday, Rep. Tom Davis of Virginia distributed a 20-page assessment of the party’s prospects, later saying it warned that following the “same-old, same-old is a 25-seat loss.”

Republicans are increasingly concerned about their election prospects after a Democrat, Travis Childers, won a Mississippi House seat Tuesday that Republicans had held for more than 13 years, the third time since March that a Democrat won a Republican-held seat in a special election.

The House Republican leader, John Boehner, said leaders planned to meet yesterday to discuss the impact of the Mississippi result. In response to a question, he said changes at the National Republican Congressional Committee, the party’s candidate recruitment and fund-raising arm, are under discussion.

“I expect we’ll discuss changes that may be necessary to address the atmosphere we’re facing,” Mr. Boehner said. He called the election result a “wake-up call,” and said the problem is that voters don’t see the Republican Party as a force for change.