Bernie Sanders on Sunday defended Hillary Clinton over recorded remarks that Republicans said demeaned his supporters but which he said were entirely in line with his beliefs.

The recording, from a 16 February fundraiser, was acquired by hackers and first published by the Washington Free Beacon this week. In it, Clinton said she feared for young people such as those who supported Sanders in the Democratic primary.

“Young people seem to be listening to promises on both sides,” Clinton said, “and I’m worried that you can’t get from here to there without going incrementally.”

In the recording, Clinton said young Americans were “children of the great recession” who were “living in their parents’ basement … feeling like you’re consigned to, you know, being a barista, or you know, some other job that doesn’t pay a lot and doesn’t have some other ladder of opportunity attached to it”.

That, she said, meant “the idea that maybe, just maybe, you could be part of a political revolution is pretty appealing”.

In such dire circumstances, she said in a reference to Sanders’ advocacy of healthcare reform on a European model, idealism had taken root as “a deep desire” to “go as far as, you know, Scandinavia, whatever that means”.

Clinton’s conclusion was an appeal to empathy: “I think we should all be really understanding of that and should try to do the best we cannot to be, you know, a wet blanket on idealism.”

By Friday, Republicans were trying to use the audio to warn young voters, who have remained wary of Clinton, away from her campaign. The Trump campaign manager, Kellyanne Conway, tweeted that Clinton had been “caught again mocking Americans; she hates coal miners, baristas, Sanders idealists”.

Sean Spicer, a spokesman for the Republican national committee, said Sanders supporters should “get out of your parents baement [sic] and listen to what Hillary Clinton thinks of you”.

On Sunday, Sanders said he was in full agreement with Clinton, whom he has endorsed and campaigned with despite their disagreements on issues such as hydraulic fracking and foreign intervention.

“I agree with her,” Sanders told CNN’s State of the Union. “There are young people who went deeply into debt, worked very hard to get a good education – they are living in their parents’ basements and that’s the point there.”

The Vermont senator urged his supporters to “take a hard look at Hillary Clinton or Donald Trump, take a hard look at the needs of the American people, issue by issue”.

He then rattled off issues on which he and Clinton both want reform, including climate change, money in politics, pay equity for women and taxes on the highest earners.

“The bottom line here is that since the [primary] election, Secretary Clinton has worked with me,” Sanders said. “Clinton is far and away the superior candidate.”

In particular, Sanders excoriated Trump over his alleged failure to pay federal income taxes, possibly for as long as 18 years after a nearly billion-dollar business loss.

“I personally do believe we do need a political revolution,” he said, “to make sure that Donald Trump and his billionaire friends start paying their fair share.”

He added: “Many of these billionaires have loopholes that these lobbyists and friends on Capitol Hill provide them. They pay zero taxes, you pay [on what you make :] 15 bucks an hour.”

This inequality, he added, “is exactly why so many millions of Americans are frustrated, they’re angry”.

Trump himself has tried to lure Sanders supporters to his side, saying “they like Trump on trade, a lot!” But younger voters have shown a preference for third-party candidates such as Libertarian Gary Johnson or Green party candidate Jill Stein.

Sanders dismissed Johnson’s recent struggles in interviews, including a failure to name a single world leader he admires, and said voters would turn away from the Libertarian on issues such as climate change, on which he has expressed skepticism.

“People who voted for me,” he said, “[will] take a hard look at what he stands for, and understand where he’s coming from, [and] will not be supporting him.”

Late on Sunday, Trump returned indefatigably to the issue, tweeting: “Bernie should pull his endorsement of Crooked Hillary after she decieved him and then attacked him and his supporters.”