By Susan Cornwell and David Lawder
WASHINGTON (Reuters) - A small but influential bloc of conservative Republicans in the U.S. House of Representatives threw its support behind a longshot candidate for House Speaker on Wednesday, complicating the party's efforts to elect John Boehner's successor.
The approximately 40-member House Freedom Caucus agreed to vote for Representative Daniel Webster in a secret nominating ballot on Thursday, showcasing its clout as it tries to push the chamber's Republican leadership to the right to battle President Barack Obama through 2016.
House Majority Leader Kevin McCarthy is considered the front-runner in Thursday's intra-party vote.
If McCarthy prevails with his fellow Republicans on Thursday but this band of conservatives continues withholding support for him, it could deny the Californian the 218 votes needed to win the speakership in a public vote scheduled for Oct. 29.
Democratic aides say their party's 188 members will not help McCarthy become speaker.
The Freedom Caucus members said the decision to support Webster on Thursday does not bind them to vote as a bloc for the Florida conservative in the full-House vote. They will reserve judgment until they hear from the winner of Thursday's ballot.
"Our intention is to go all the way to the floor (with Webster) unless real changes are made in how the House is run," Representative Raul Labrador told reporters after the group met on Wednesday.
Labrador said more than 30 of the group's members voted for Webster, meeting its 80 percent threshold for policy decisions.
Webster, 66, was first elected to Congress in the Tea Party wave of 2010 and was speaker of the Florida House of Representatives in the 1990s. Freedom Caucus members said he was best positioned to make the changes they want, with committees given more power over legislation and fewer backroom deals pushed onto the floor by their leaders.
The Freedom Caucus, formed this year by members sympathetic to the small government Tea Party movement, was instrumental in pressuring Boehner to resign after they fought a series of internal party battles with him, most recently demanding that a government funding bill deny money to women's health care group Planned Parenthood.
McCarthy for the past year has been seen as heir apparent to Boehner, who is stepping down at the end of October. In recent days McCarthy has sought to differentiate himself from his former mentor.
But if he cannot persuade enough conservatives to back him, the transition could prove messy, requiring additional ballots and a potentially damaging fight among Republicans as the presidential election campaign ramps up. McCarthy also faces another challenger, House Oversight Committee Chairman Jason Chaffetz.
Another House conservative, Representative Walter Jones, injected a new wrinkle into the leadership race, requesting that all candidates confess any personal "misdeeds" that could embarrass the party. He did not name any specific concerns, and a spokeswoman was not immediately available to elaborate.
In a letter to party leaders, Jones recalled past personal controversies, such as the resignation of Speaker-elect Bob Livingston in 1998 after an extramarital affair became public.
(Reporting by Susan Cornwell; Writing by David Lawder; Editing by Richard Cowan and Richard Chang)