Singer Ariana Grande appeared to throw her weight behind Sen. Bernie Sanders, I-Vt., on Wednesday, tweeting that he had attended one of her concerts on Tuesday.

"MY GUY," Grande tweeted alongside photos of her and the 2020 candidate. "[T]hank you Senator Sanders for coming to my show, making my whole night and for all that you stand for !" she added before saying she will "never smile this hard again promise."

Grande said she was trying to make Sanders "proud" by registering voters with HeadCount, an organization that claims to work "with musicians to promote participation in democracy."

"@headcountorg and i [sic] are doing our best to make you proud. we’ve already registered 20k+ young voters at my shows alone. also i [sic] will never smile this hard again promise," she said.

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Sanders, for his part, praised Grande on Twitter, describing her as an "outstanding advocate for social justice."

"We must all be prepared – like Ariana has shown – to fight for everyone who is struggling. It was great to meet her in Atlanta last night," he said.

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Sanders previously played off of lyrics that she tweeted in October. "[B]aby how u feelin," Grande tweeted.

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"Ready to fight for Medicare for All," Sanders tweeted in response. Rep. Alexandria Ocasio-Cortez, D-N.Y., who has endorsed Sanders, added to the conversation with a list of songs she suggested could be used to promote progressive policies.

Grande's apparent endorsement came as the Vermont senator fell behind former Vice President Joe Biden and, in some polls, Sen. Elizabeth Warren, D-Mass. Sanders has consistently ranked among the top tier candidates for the Democratic nomination and received endorsements from three members of the "Squad" of progressive congresswomen in the House.

Sanders also received public backing from rapper Cardi B, who suggested in July that he should have won the Democratic nomination in 2016.

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"I been reading about Bernie Sanders and I’m really sad how we let him down in 2016," she wrote on Twitter. The rapper then pointed to Sanders' longtime passion for "equal rights, HUMAN rights."

"Seeing this country become a better place been really his passion for a long time not a new front for a campaign," she continued.