Democratic presidential candidate Bernie Sanders is facing a backlash after he touted a thumbs-up from a podcast host loathed by many liberals.
Joe Rogan, a comedian turned provocateur, has told his seven million YouTube subscribers that he would "probably vote for Bernie".
Amid the ensuing outcry, Mr Sanders said his campaign was "a big tent".
Mr Rogan has previously drawn criticism for making what some consider sexist and transphobic comments.
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'I like him a lot'
In a video on his show, The Joe Rogan Experience, the YouTube star said he likes Mr Sanders because the Democrat has been "insanely consistent his entire life".
"I like him a lot," he said.
"He's basically been saying the same thing, been for the same thing his whole life. And that in and of itself is a very powerful structure to operate from," Mr Rogan says of the septuagenarian Vermont senator.
The clip was tweeted by the Sanders campaign and has been watched over four million times.
However, the decision to highlight the association with Mr Rogan provoked criticism from some of Mr Sanders's backers.
In particular there has been heavy criticism from some transgender women, who have labelled Mr Rogan "transphobic" over previous comments he has made on his show.
Mr Rogan once said that a transgender woman was not "an actual woman".
He has also been criticised for interviewing controversial figures such as Alex Jones, a conspiracy theorist.
Others thought Mr Rogan's backing could help Mr Sanders gather more support.
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The blowback risk is real
Analysis by Anthony Zurcher, BBC Washington
It wasn't a full-throated endorsement. In fact, "I think I'll probably vote for Bernie … I like him a lot" wasn't much of an recommendation at all. But there's a reason Bernie Sanders is touting Joe Rogan's comments - even at the risk of provoking anger from some of his left-wing supporters.
Rogan has a loyal following of millions of men, many of whom aren't particularly political and might be open to a Sanders campaign built around his us-against-the-system economic populism. It represents a largely untapped pool of potential voters in the Democratic primaries - ones who may have voted for Donald Trump's establishment-smashing pitch in 2016 and are shopping around again this year.
The blowback risk to Sanders is real, however. Some of Rogan's past comments have been viewed as derogatory toward women. Given that Sanders critics - including, most recently, 2016 opponent Hillary Clinton - have said the Vermont senator has been too tolerant of misogyny among his followers, his celebration of the Rogan endorsement could amplify those concerns.
Sanders is walking a fine line - but in a tight race just over a week before the first primary contest starts, he appears to have deemed the potential to expand his electoral coalition to be worth the risk.
Responding to the backlash, the Sanders campaign said it is trying to "build a multi-racial, multi-generational movement that is large enough to defeat Donald Trump".
"Sharing a big tent requires including those who do not share every one of our beliefs while always making clear that we will never compromise our values," the campaign statement continued.
Mr Sanders previously appeared as a guest on the Rogan podcast in August 2019.
Andrew Yang and Tulsi Gabbard, two other 2020 Democratic hopefuls, have also appeared on The Joe Rogan Experience.
Mr Rogan has since said that representatives for three other Democratic contenders, Elizabeth Warren, Joe Biden and Pete Buttigieg, had been touch about an appearance.
But he said he would not invite them on to the show because he would "rather talk to my friends", adding: "I like Tulsi and I like Bernie. That's it."
Mr Rogan is not formally affiliated with any particular political party, and his show has featured guests with varying political views.