Senate Majority Leader Sen. Mitch McConnell (R-Ky.), shown Tuesday at the Capitol, said of his party’s presidential nominee Donald Trump: “On the debate, I thought he did just fine.” (Alex Wong/Getty Images)

Leading Republicans vented frustration Tuesday that the first presidential debate was a missed opportunity for Donald Trump to magnify Hillary Clinton’s biggest vulnerabilities, lamenting the lack of focus on her personal email server, the Clinton Foundation and the deadly attacks in Benghazi, Libya.

On Capitol Hill, some GOP members of Congress blamed Trump for not raising the issues with more frequency and intensity. Others held moderator Lester Holt responsible for not pressing Clinton harder. Some normally chatty members kept quiet altogether.

“If anything, I think he held back in a few instances where maybe he should have gone on the attack,” said Sen. Thom Tillis (R-N.C.), a Trump supporter.

The reactions reflected a collective sense of deflation among Republicans after a rough night when Clinton repeatedly lured Trump into defending himself and lobbing tangential personal attacks against her and others, rather than sticking to the case he has been prosecuting with more discipline in recent weeks.

“I don't think there was probably as fulsome a discussion as there could have been last night because they did get off on some other issues,” said Sen. John Thune (R-S.D.), who backs Trump.

The Post's Fact Checker rounded up the most noteworthy claims, misstatements, exaggerations and falsehoods from Hillary Clinton and Donald Trump during the first presidential debate on Sept. 26. (Jenny Starrs/The Washington Post)

In the end, it was Clinton who walked away with an abundance of fresh fodder for attack ads, including one she launched online Tuesday featuring a former Miss Universe winner explaining how Trump insulted her for gaining weight — an attack he repeated in a Fox News interview Tuesday morning.

In speeches, conference calls and photo-ops staged in the fortnight leading up to the debate, Trump and his campaign waged a meticulous effort to draw attention to Clinton’s missteps, including her labeling of half of Trump’s supporters as a “basket of deplorables.”

But during the debate in Hempstead, N.Y., he didn’t once utter the words. And while he mentioned Clinton’s use of a private email server as secretary of state, calling on her to release thousands of emails she said were personal and deleted, he missed a chance to raise it again during a question about cybersecurity.

“As far as the cyber, I agree to parts of what Secretary Clinton said. We should be better than anybody else, and perhaps we’re not,” Trump said, before talking about unflattering leaked emails from the Democratic National Committee.

While a criminal probe led to no charges against Clinton for her email practices, Republicans have held up her secretive approach and questionable handling of sensitive material as a chief reason she cannot be trusted. Polls have shown that the issue worries voters as well.

“For her to get a pass and act like she’s gotten past it, I don’t think that’s appropriate,” Tillis said. “I think those are the sorts of things that he should continue to make the American people remind them[selves] of, because I think it’ll be consequential in November.”

Sen. David Perdue (R-Ga.), one of Trump’s most vocal advocates on Capitol Hill, said Trump did the best he could under difficult circumstances.

Hillary Clinton on Sept. 26 scolded Donald Trump for his previous comments on women using language that was nearly identical to a question that Fox News anchor Megyn Kelly asked him more than a year ago. (The Washington Post)

“The moderator has a tough job. But I think you’ve got some — the priority issues, the debt, the economy, jobs, the foreign policy crisis. And you’ve got all these things that weren’t talked about — the Benghazi situation, her emails, the foundation. I’m really troubled that we didn’t get there in this debate.”

At one point in the debate, it appeared that Trump might have been gearing up to attack Clinton over the deaths of four Americans in the 2012 assault on the U.S. diplomatic mission in Benghazi. Instead, the two sparred over the invasion of Iraq and the formation of the Islamic State.

Speaking Tuesday morning, Trump knocked Holt for the way he handled the role of moderator.

“Well, he didn’t ask her about the emails at all. He didn’t ask her about her scandals. He didn’t ask her about the Benghazi deal that she destroyed,” Trump said on Fox News. “He didn’t ask her about a lot of things that she should have been asked about. I mean, there’s no question about it. He didn’t ask her about her foundation. Why? I don’t know.”

One of Trump’s central charges against Clinton is that she has manipulated her positions of authority for financial gain — “Crooked Hillary,” as he calls her on the campaign trail. But Trump did not mention the Clinton Foundation at all, which has been at the center of conservatives’ accusations that she traded access for donations as secretary of state.

Some Republicans kept their post-debate reviews remarkably brief on Tuesday.

Senate Majority Leader Mitch McConnell (R-Ky.) offered a nine-word assessment at an afternoon news conference: “On the debate, I thought he did just fine.”

“I didn’t see it, guys. I was on an airplane,” said Sen. Marco Rubio (R-Fla.), one of Trump’s vanquished primary foes, who now supports him.

Sen. Ted Cruz (R-Tex.), another Trump rival-turned-backer, repeatedly brushed off debate questions. In an earlier interview with conservative host Hugh Hewitt, Cruz said he would have liked to have heard more discussion about the Supreme Court.

Many Republicans, particularly those who are not hardcore Trump supporters, have pointed to the vacancy on the court as an incentive to support him over Clinton.

However, Trump did not bring it up once Monday night. Separately — and inexplicably to some Republicans — Trump reignited his feud with Rosie O’Donnell, saying the comedian and actress deserved the criticism he has directed at her.

Clinton came to the debate prepared to steer the discussion toward her preferred topics. She introduced the tens of millions watching to Alicia Machado, the 1996 Miss Universe winner from Venezuela who has said Trump called her “Miss Piggy” and “Miss Housekeeping.”

“She gained a massive amount of weight, and it was a real problem. We had a real problem,” Trump told Fox News Tuesday.

Democrats sounded confident that the debate showcased the portrait they are painting of Trump as an unpresidential loose cannon.

“Anybody who comes unhinged like he did over 90 minutes — that’s not who you want in pressure-cooker situations, because he’s clearly not up to handling it,” said Sen. Claire McCaskill (D-Mo.), a Clinton supporter.

Paul Kane and Jenna Johnson contributed to this report.