WASHINGTON – In eight concise paragraphs, two moderate and two conservative House Republicans put into writing last week what they say many of their colleagues quietly fear: the GOP’s plunging poll numbers, the rising public support for a Congress controlled by Democrats, and the increasing belief among voters that the Republican Party is corrupt.

House Republicans will gather Thursday to elect a successor to Rep. Tom DeLay, a Republican of Texas, as majority leader, and the perceptions of corruption, though “neither fair nor accurate … are reality,” Reps. Jim Kolbe, of Arizona, Charles Bass, of New Hampshire, Paul Ryan, of Wisconsin, and Tom Feeney, of Florida, wrote in a letter to their colleagues, imploring them to vote for change. “We must realize that the Majority we have all worked so hard for is in jeopardy.”

It is not clear how widespread such fear is on Capitol Hill, with Congress in recess, but it has shaped the campaigns of Reps. John Boehner, of Ohio, and John Shadegg, of Arizona, as they try to derail the front-runner – the majority whip and acting majority leader, Rep. Roy Blunt, of Arizona – in a race that has taken on enormous significance.

Mr. Blunt aides insist their boss, running as the candidate of continuity and proven leadership, has the race wrapped up, with more than enough committed supporters to hand him a swift victory on the first ballot. Mr. Blunt’s chief deputy whip, Eric Cantor, of Virginia, has said he also has the votes to move up to the whip’s job, if Mr. Blunt vacates the post to become majority leader.

But supporters of Mr. Blunt’s opponents say the acting majority leader has stumbled badly in recent days, as Messrs. Boehner and Shadegg push to

turn the leadership contest into a referendum on how seriously the party is taking a corruption scandal that has already led to the conviction of one Republican House member and a former GOP lobbyist, Jack Abramoff. A vote for Mr. Blunt to succeed the indicted DeLay and, for that matter, Mr. Cantor to succeed Mr. Blunt as whip, would send precisely the wrong message, supporters of Messrs. Boehner and Shadegg say.

An internal leadership race is often won or lost not on big themes such as reform and continuity but on personal relationships and promises made to individual lawmakers. But this week’s contest may be different, say strategists for all three candidates. It is taking shape before a backdrop of scandal and in an election year when Democrats see their best chance of regaining control of the House in years.

A Blunt victory probably would keep the year’s legislative agenda focused on themes already voiced by the existing leadership team: immigration law changes, a restructuring of congressional lobbying rules, and fiscal discipline. A victory by either Mr. Boehner or Mr. Shadegg could lead to a significant change of direction, fortifying conservative forces that want to radically curtail home-district pork-barrel spending, cut down the size of government, and resume pushing power to state and local governments.

Messrs. Boehner and Shadegg both say they can win the campaign outright, but an unspoken alliance between the two appears aimed at denying Mr. Blunt a majority vote in the first round of voting. The third-place finisher could then endorse the runner-up to defeat Mr. Blunt in the next round of voting.

Mr. Blunt’s supporters say the drumbeat for “reform” smacks of unnecessary panic.

With 92 declared supporters, Mr. Blunt remains the favorite, well ahead of Mr. Boehner’s 49 declared supporters and Mr. Shadegg’s 16. But House members and advisers say the race remains more open than it looks.