Sanders supporters gathering at City Hall in downtown Philadelphia
Sanders supporters gathering at City Hall in downtown PhiladelphiaJeff J Mitchell/Getty Images

A newly-released audio recording of a primary season meeting with supporters is threatening to hurt Clinton with a much-needed voter demographic this November, and give the Trump campaign some much-needed ammunition after a week of post-debate troubles for the Republican candidate.

On Friday, The Washington Free Beacon released an audio recording of the Democratic nominee during a February primary season fundraiser in Virginia.

During the event, Mrs. Clinton attempted to cast herself as a centrist alternative to what she described as the “populist, nationalist xenophobic” approach of then-GOP frontrunner Donald Trump, and a naïve, “democratic-socialist” vision espoused by Vermont Senator Bernie Sanders.

Sanders, who won strong backing from younger voters and independents, offered a grab-bag of government-funded benefits, including tuition-free college and an expansion of the Medicare system to cover all Americans.

While Clinton maintained a narrow lead over Sanders through the primary season and eventually secured the party’s nomination, she has failed to draw strong support from Millennial voters – a group that overwhelmingly backed President Obama both in 2008 and 2012.

In an attempt to energize support from younger voters, Clinton has borrowed some elements of Sanders’ platform, calling for, among other things, tuition-free college for low- and middle-income families.

But in the newly-released recording of Mrs. Clinton, the former Secretary of State dismisses the ideas advocated by Sanders, and writes off his supporters as political neophytes who fail to understand the complexities of economics.

“Some are new to politics completely,” Clinton said of Sanders supporters. “They’re children of the Great Recession. And they are living in their parents’ basement.”

“There’s just a deep desire to believe that we can have free college, free healthcare, that what we’ve done hasn’t gone far enough, and that we just need to, you know, go as far as, you know, Scandinavia, whatever that means, and half the people don’t know what that means, but it’s something that they deeply feel.”

The recording was reportedly unearthed by hackers who took emails from the account of a campaign staffer.

The comments drew harsh criticism from some Sanders backers, who lit up social media with the hashtag “#Basementdwellers”.

The Trump campaign pounced on the recording, comparing it Clinton’s recent “basket of deplorables” attack on supporters of the Republican nominee.

“Crooked H is nasty to Sanders supporters behind closed doors,” tweeted Trump. “Owned by Wall St and Politicians, HRC is not with you.”

“Who else does @HillaryClinton ridicule behind closed doors for $$$?”, added Trump campaign manager Kellyanne Conway.

A Clinton campaign rep suggested the former First Lady was encouraging young voters to “set big goals”, rather than dismissing them.

“She wants young people to be idealistic and set big goals,” said Glen Caplin.