Massachusetts Senator and Democratic presidential candidate Elizabeth Warren stumbled when asked about a purity test put forward by Independent Vermont Senator Bernie Sanders, who boasts that his is the only campaign to “receive no contributions from billionaires.”

While campaigning in Nevada on Monday, Sanders told the crowd he is “proud to tell you, I think we are the only campaign to have received no contributions from billionaires.”

Sanders has been spurning donations from billionaires for quite some time, and in November, even returned a $470 donation from a billionaire. But his claim to be the only campaign to do so caught the attention of CBS News reporter Zak Hudak, who confronted Warren about it.

Hudak told Warren that Sanders “has said he has not taken donations from billionaires,” and asked “why have you not made that same pledge?”

“Wait, I’m sorry, he said what?” Warren asked.

“That he’s the only candidate that’s not taking donations from billionaires,” Hudak repeated.

“Look, I don’t sell access to my time. Period. I’ve done all of my fundraising that I’ve been engaged in online, I’ve made my call time entirely to people who make $5 and $10, $25 donations,” Warren said, adding “Because I believe that the way we’re going to win in 2020 is to build a grassroots movement all across this country, and that’s exactly what I’ve been doing.”

“Would you consider making the same pledge?” Hudak asked.

“I don’t even know what that means,” Warren said, then repeated “Like I said, I don’t sell access to my time and that’s been true since the very first day I got in this campaign. And I think it’s a serious problem. Candidates who sell access to their time are running a very different kind of campaign.”

“I don’t even know what that means. Like I said, I don’t sell access to my time, & that’s been true since the first day I got in this campaign,” @ewarren told me the other day on @BernieSanders⁩ saying he’s the only candidate not taking billionaire $ and whether she’d do same pic.twitter.com/AUgEYKmYvD — Zak Hudak (@cbszak) December 11, 2019

Warren has been warring with South Bend Mayor Pete Buttigieg recently on a variety of issues including fundraising, and Buttigieg has responded by meeting Warren’s demands for more transparency.

But the Massachusetts senator has been attacking other candidates over fundraising for longer than that, promising in October to swear off any and all high-dollar fundraising events, only to later clarify that she will headline such events in the general election on behalf of the Democratic National Committee.

Sanders’ boast steps things up a notch, however, since Warren’s current presidential campaign has accepted donations at or near the $2800 individual contribution limit from at least six billionaires. Perhaps Warren can outflank Bernie by not accepting any donation that hasn’t been scanned for billionaire DNA.

Watch the clip above, via Zak Hudak.

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