Sen. Bernard Sanders gave Democratic presidential nominee Hillary Clinton a pass Sunday for disparaging his young supporters during the primary in condescending terms as overly idealistic political newbies who “live in their parents’ basement.”

Mr. Sanders, who led a far-left movement that was the biggest challenge to Mrs. Clinton during the primary but now supports her, refused to criticize Mrs. Clinton’s condescending description.

“What she was saying there is absolutely correct,” Mr. Sanders said on ABC’s “This Week.”

A recording from a February fundraiser, which was first reported Friday by the Washington Free Beacon, caught Mrs. Clinton saying that Mr. Sanders‘ supporters were overly idealistic and had unrealistic expectations for a left-wing political revolution.

“They’re children of the Great Recession, and they are living in their parents’ basement. And so if you’re feeling that you are consigned to, you know, being a barista or, you know, some other job that doesn’t pay a lot and doesn’t have much of a ladder of opportunity attached to it, then the idea that maybe, just maybe, you could be a part of a political revolution is pretty appealing,” she says on the audio recording.

The leaked receding from a February fundraiser further complicated Mrs. Clinton’s struggle to attract young voters, whose reluctance to support her has hobbled her attempt to rebuild President Obama’s hope-and-change coalition.

Republican nominee Donald Trump, who has been attempting to woo Mr. Sanders‘ supporters to his anti-establishment run, said the recording reveals Mrs. Clinton’s two-faced nature.

“Hillary Clinton thinks Bernie supporters are hopeless and ignorant basement-dwellers,” Mr. Trump said at a rally Saturday in Pennsylvania.

The New York billionaire also tweeted about the recording: “Crooked H is nasty to Sanders supporters behind closed doors. Owned by Wall St and Politicians, HRC is not with you.”

But Mr. Sanders, a self-described democratic socialist from Vermont who mounted a powerful challenge to Mrs. Clinton in the primary, said he “took it exactly the opposite way,” while acknowledging that he and Mrs. Clinton do disagree on some issues.

After she clinched the nomination, he got behind her run and has urged his fans to do the same.

“I think that’s a very important point and that is an issue that, as a nation, we have got to address,” he said. “How do we create good-paying jobs for people who have a decent education?

“And one of the issues that Clinton is talking about is rebuilding our infrastructure, pay equity for women, raising the minimum raise to a living wage so, in fact, we can have decent-paying jobs for all of our people,” said Mr. Sanders.

The leaked recording of Mrs. Clinton was reminiscent of 2012 Republican nominee Mitt Romney’s “47 percent” comment, in which he was recorded at a fundraiser saying that Mr. Obama will inevitably get the support of the 47 percent of Americans who don’t pay taxes and disparaging attempts to win them over.

Mr. Romney’s remarks were credited with cementing his image as a wealthy elitist.

Mrs. Clinton’s remarks were in line with her rhetoric during the campaign, in which she criticized Mr. Sanders‘ positions as unrealistic. She called herself a progressive who “gets things done.”

In the recording, Mrs. Clinton also criticized Americans on the right who support Mr. Trump. She called their political perspective a “populist, nationalist, xenophobic, discriminatory kind of approach” compared to the left-wing’s yearning for “free college, free health care” and to “go as far as, you know, Scandinavia.”