House Majority Leader Kevin McCarthy at the John Hay Initiative in Washington Monday. (Jacquelyn Martin/AP)

So now we know: One of the principal reasons Republicans spent so much public money investigating the tragic Benghazi episode was to bring down Hillary Clinton’s poll numbers.

Majority Leader Kevin McCarthy (R-Calif.), the likely successor to House Speaker John Boehner (R-Ohio), told Fox News’s Sean Hannity explicitly on Tuesday night that the Clinton investigation was part of a “strategy to fight and win.”

He explained: “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 untrustable. But no one would have known any of that had happened, had we not fought.”

The Republican-led House hasn’t been particularly good at governing, but perhaps governing has never been the point. Why govern when there’s a future election to influence?

No doubt Republicans will clean up after McCarthy’s comments by insisting that the politics were a side benefit from a necessary investigation. But it would be nice to know more about the House GOP’s internal deliberations as it launched one inquiry into Clinton after another. Did we need another investigation by the select committee headed by Rep. Trey Gowdy (R-S.C.)? After all, a two-year investigation by the Republican-controlled House Intelligence Committee cleared the military and the CIA of improper behavior in response to the 2012 attack on the diplomatic compound in Benghazi, Libya.

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. (Alice Li/The Washington Post)

Taxpayers might be interested in learning whether their hard-earned money — sorry, I could not resist invoking that favorite GOP cliche — was going out the door primarily to affect the chances of one particular candidate for president. How much? Rob Garver of the Fiscal Times has estimated that the select committee “will likely spend some $6 million by next year.”

McCarthy’s statement does not make Clinton’s problems disappear miraculously. She has suffered damage, some of it self-inflicted, from using a private e-mail server during her time at the State Department. Clinton herself has acknowledged that she should have used a government server. Almost no one in her own party believes that she handled the ensuing controversy particularly well. She has recalibrated her response in recent weeks, accepting that she has to answer the questions and meet the challenges thrown her way from journalists and political foes alike.

Fine. But McCarthy’s statement gave Democrats what they have long sought: a rather strong public hint that this investigation was never on the level. “This stunning concession from Rep. McCarthy reveals the truth that Republicans never dared admit in public,” said Rep. Elijah Cummings (Md.), the committee’s ranking Democrat. “The core Republican goal in establishing the Benghazi committee was always to damage Hillary Clinton’s presidential campaign and never to conduct an evenhanded search for the facts.” Clinton’s defenders hope McCarthy’s statement might prod the media to pay attention to the current behavior of the accusers and not just the past behavior of the accused.

McCarthy’s admission once again ratified the writer Michael Kinsley’s long-ago but still brilliant observation that a gaffe occurs “when a politician tells the truth — some obvious truth he isn’t supposed to say.” But why did McCarthy do it? Consider the nature of the House Republican Party he’d like to lead.

The main objection of right-wingers in the House to Boehner and their other leaders is that they have not been tough enough as partisans and ideologues. As Rep. Peter Roskam (R-Ill.), told The Post’s Robert Costa and Mike DeBonis: “We’d be in better shape if we were more rhetorically aggressive with the administration.”

Now, perhaps I lack imagination, but I don’t know how much more rhetorically aggressive the House GOP could be with President Obama than it has already been — short of accusing the entire administration of treason. But McCarthy wants to mollify the right end of his caucus (and the conservative talk-show complex), so notice the end of his statement emphasizing how Republicans had “fought” to bring Clinton’s numbers down. See, McCarthy was telling his party’s ultras, we’ve been really, really partisan — and effective, too. And I’m sure McCarthy was pleased when Hannity gave him a pat on the back. “That’s something good,” Hannity said. “I give you credit for that.”

Bill and Hillary Clinton have been lucky over the years in having a cast of characters arrayed against them who always overplayed their hand. McCarthy, who kept a poker table in his Sacramento house during his days in the California legislature, went all in a bit too early.

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