Rep. Kevin McCarthy appeared on Fox News Channel and commented on the Select Committee on Benghazi, suggesting the panel and its investigation brought Hillary Clinton's poll numbers down. Washington Post reporter Elise Viebeck explains why McCarthy's comment ended up getting him in trouble and being a win for Clinton. (Alice Li/The Washington Post)

Hillary Rodham Clinton’s upcoming appearance before the U.S. House Select Committee on Benghazi was supposed to be a crucible: a chance for Republicans to prosecute the former secretary of state for her handling of the 2012 terrorist attacks that killed four Americans as well as for her use of a private e-mail server.

Instead, it may have turned into a political gift for Clinton following this week’s suggestion by the likely next House speaker, Majority Leader Kevin McCarthy (R-Calif.), that the taxpayer-funded Benghazi investigation was politically motivated. Clinton’s allies say his comments will help recast Clinton’s scheduled Oct. 22 hearing as a partisan inquisition rather than a fact-finding mission about the attacks in Libya.

McCarthy boasted in two television interviews on Tuesday that the committee’s work already had achieved a desired result: Clinton’s decline in the polls. The statements riled Democrats by seeming to validate their suspicions about the probe, which led to the discovery of Clinton’s use of a private e-mail server — a controversy that has dogged her for seven months.

“The Benghazi committee has been a huge part of the e-mail story from the beginning, so it takes the entire e-mail story and admits to everybody that it’s in a political context,” said Steve Elmendorf, a Clinton supporter and former House aide. “Now I don’t know what they can do to make that hearing at all successful for Republicans.”

As strategist James Carville, a longtime Clinton ally, put it, “The thermostat has changed.”

Catch up on the controversy and read the emails

The select committee’s chairman, Rep. Trey Gowdy (R-S.C.), has maintained that its work was a neutral examination of the Sept. 11, 2012, attacks. But McCarthy told Fox News host Sean Hannity: “Everybody thought Hillary Clinton was unbeatable, right? But we put together a Benghazi special committee, a select committee. What are her numbers today? Her numbers are dropping. Why? Because she’s un-trustable. But no one would have known any of that had happened had we not fought.”

On Thursday morning, Senate Democratic leaders called on House Speaker John A. Boehner (R-Ohio) to disband the committee. Boehner defended its work and insisted its aim is to “know the full truth about what happened” and “never” has been about Clinton.

On Thursday night, McCarthy said on Fox News that he had apologized to Gowdy and regrets his comments. “It was never my intention to ever imply that this committee was political, because we all know it is not,” he said.

McCarthy’s Tuesday comments on Fox News — which echoed remarks from a CNN interview earlier that day — raised concern among congressional Republicans about his political skills and preparedness to ascend to the top leadership position on Capitol Hill when Boehner steps down on Oct. 30.

“He has to learn a lesson which I found very difficult: When you move up to speaker, everything you say is like being a presidential candidate,” said former House speaker Newt Gingrich (R-Ga.). “Everything you say is national, everything you say is subject to scrutiny, and you simply have to be careful to say precisely what you intend and nothing more or less. It’s a transition problem.”

The affable McCarthy has cultivated tight relationships with fellow Republicans and has tended to internal House affairs. But with relatively scant legislative experience, McCarthy is now trying to step forward as a competent and politically sharp leader of his party.

Regardless, the controversy is unlikely to rupture McCarthy’s campaign for the top job. His lone opponent ahead of next Thursday’s leadership elections, Rep. Daniel Webster (R-Fla.), is a little-known conservative who won only 12 votes on the House floor when he tried to challenge Boehner earlier this year.

Rep. Trey Gowdy (R-S.C.), chairman of the House Select Committee on Benghazi, heads to hear closed testimony last month from former Clinton aide Cheryl Mills about the Benghazi attacks. (Jim Lo Scalzo/EPA)

“This is one of those blips you wish hadn’t happened, but it’s not hurtful or crippling to McCarthy,” said Rep. Tom Cole (R-Okla.). “The real driver of this story isn’t what any Republican congressman said; it’s the e-mails and the server.”

With Clinton struggling to gain momentum in the Democratic nominating fight, McCarthy’s comments amount to a unifying force for the party to rally to her defense, as well as give her an opening to do what she is most comfortable doing: fighting back against Republicans.

“I think it will pull people together,” said Dan Pfeiffer, a former senior adviser to President Obama. “The e-mail situation is a complicated one. . . . All of that is gobbledygook to the American people, but political motivation is easily understood.”

David Brock, a Clinton ally who runs an assortment of Democratic groups that have aggressively defended her, said McCarthy’s suggestive comment “changes everything entirely.”

“To put it simply, the game is over, and they’ve lost,” Brock said. “This was supposed to be the big moment for Gowdy and his committee and instead what we have is the person who’s likely the next speaker validating everything critics have been saying. . . . Now everyone can see the fact that this has been a partisan charade all along.”

Looking ahead to the general election, Brock added: “With this clip, we now have the ad we want.”

Clinton and her campaign have responded aggressively. On Wednesday, she said in an interview with MSNBC host Al Sharpton that McCarthy’s comments were “deeply distressing.”

“When I hear a statement like that, which demonstrates unequivocally that this was always meant to be a partisan political exercise, I feel like it does a grave disservice and dishonors not just the memory of the four that we lost, but of everybody who has served our country,” Clinton said.

On Thursday, her campaign pushed out a video to supporters in which press secretary Brian Fallon, speaking from Brooklyn headquarters, says McCarthy exposed “a political farce.”

“This is a big deal,” Fallon says in the video. “This committee, masquerading as an attempt to look into the deaths of four brave Americans we lost at Benghazi, is actually a taxpayer-funded sham and they’re focused on only one thing: driving down Hillary Clinton’s poll numbers.”

On Capitol Hill on Thursday, GOP lawmakers called the episode a wake-up call and learning experience for McCarthy — and said he still needed to douse the fires.

“Kevin should call it back and say it was an obvious mistake,” said Rep. Peter King (R-N.Y.), a Boehner ally. “You give Bill and Hillary Clinton an issue and they’re going to run with it. You’ve got to be on your guard and realize this is the big leagues, the World Series, and every error is magnified.”

Rep. Jason Chaffetz (R-Utah), a committee chairman and close friend of Gowdy’s, said Thursday on MSNBC that McCarthy’s comments were “just absolutely inappropriate. They should be withdrawn. Mr. McCarthy should apologize.”

Other Republican lawmakers were less agitated, however. Rep. Steve King (R-Iowa) said there was no need for McCarthy to apologize — a view he said other conservatives share.

“When I heard what he said, it didn’t light me up at all,” King said. “There is nothing wrong with saying that Benghazi has a political effect.”