Donald Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE on Tuesday accused Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE of not staying "true to himself and his supporters" and having "sold out" to Hillary Clinton Hillary Diane Rodham ClintonBiden leads Trump by 36 points nationally among Latinos: poll Democratic super PAC to hit Trump in battleground states over coronavirus deaths Battle lines drawn on precedent in Supreme Court fight MORE, hours before Sanders is expected to endorse Clinton for president.

Bernie Sanders, who has lost most of his leverage, has totally sold out to Crooked Hillary Clinton. He will endorse her today - fans angry! — Donald J. Trump (@realDonaldTrump) July 12, 2016

I am somewhat surprised that Bernie Sanders was not true to himself and his supporters. They are not happy that he is selling out! — Donald J. Trump (@realDonaldTrump) July 12, 2016

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Clinton and Sanders are slated to appear at their first joint rally in Portsmouth, N.H., on Tuesday, where many expect the Vermont senator to endorse Clinton.

Republicans have lined up to attack both Democrats, after the two faced off in a long and heated presidential primary.

The Republican National Committee riffed on Sanders's "Feel the Bern" campaign slogan, emailing reporters Tuesday with several of Sanders's attacks on Clinton during the primary and adding, "Feel the sell out."

Clinton became the presumptive Democratic nominee in early June after securing the necessary backing from delegates. Sanders has spent weeks continuing to push for progressive issues, and Clinton formally adopted a more progressive stance on healthcare in a proposal released over the weekend.

Trump, the presumptive Republican nominee, has made several pitches in recent months to supporters of Sanders, calling on them to instead back his campaign over Clinton's.