Shortly after throwing his support behind his former primary rival on Tuesday, Sen. 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 took to Twitter to mock presumptive GOP nominee 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 for criticizing the endorsement.

"Big talk from the same guy who was too afraid to debate Bernie in California," said a tweet on Sanders's campaign account, responding to a message from Trump that said Sanders had "totally sold out to Crooked 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."

Big talk from the same guy who was too afraid to debate Bernie in California. https://t.co/LVCjo0PKrN — Bernie Sanders (@BernieSanders) July 12, 2016

Trump shot back with several more tweets slamming Sanders for his endorsement of Hillary Clinton and inviting the Vermont senator's supporters to back the Trump campaign.

Bernie Sanders endorsing Crooked Hillary Clinton is like Occupy Wall Street endorsing Goldman Sachs. — Donald J. Trump (@realDonaldTrump) July 12, 2016

Bernie sanders has abandoned his supporters by endorsing pro-war pro-TPP pro-Wall Street Crooked Hillary Clinton. — Donald J. Trump (@realDonaldTrump) July 12, 2016

Sanders earlier Tuesday endorsed the presumptive Democratic nominee, effectively ending his own long primary campaign against Clinton.

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“Secretary Clinton has won the Democratic nominating process, and I congratulate her for that,” Sanders said Tuesday.

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“She will be the Democratic nominee for president, and I intend to do everything I can to make certain she will be the next president of the United States.”

In May, Sanders pressured Trump to debate him ahead of the California primaries, but Trump refused, saying it would be "inappropriate."

Trump has made several pitches to Sanders supporters in recent months, encouraging them to back his campaign instead of Clinton's.