Former FBI Director James Comey James Brien ComeyBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Michael Cohen book debuts at top of bestseller list Trump offered Kelly FBI director's job, demanded loyalty: report MORE on Super Tuesday endorsed former Vice President Joe Biden Joe BidenThe Memo: Warning signs flash for Trump on debates Senate Republicans signal openness to working with Biden National postal mail handlers union endorses Biden MORE in the Democratic primary, but Biden's campaign cheekily asked to "return" the endorsement.

“Yes, customer service? I just received a package that I very much did not order,” Andrew Bates, director of rapid response for Biden’s campaign wrote on Twitter in response to Comey's endorsement. “How can I return it, free of charge?”

Yes, customer service? I just received a package that I very much did not order. How can I return it, free of charge? https://t.co/NK4VrYGzT1 — Andrew Bates (@AndrewBatesNC) March 3, 2020

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Comey, who left the Republican Party over Trump in 2018, voted in his first Democratic primary on Tuesday, tweeting that he supports the party "dedicated to restoring values” to the White House.

He shared the words of Sen. Amy Klobuchar Amy KlobucharEPA delivers win for ethanol industry angered by waivers to refiners It's time for newspapers to stop endorsing presidential candidates Biden marks anniversary of the Violence Against Women Act, knocks Trump and McConnell MORE (D-Minn.), who endorsed Biden after ending her own Democratic bid.

“I agree with @amyklobuchar: We need candidate who cares about all Americans and will restore decency, dignity to the office,” Comey wrote. “There is a reason Trump fears @joebiden and roots for Bernie. #Biden2020.”

The president has said he thinks Sanders has emerged as the front-runner, saying “people like his message. He’s got energy, his people have energy.”

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Trump on Monday claimed the Democratic primary is “rigged” against Sanders and speculated that candidates who had dropped out of the race — including Klobuchar and former South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBogeymen of the far left deserve a place in any Biden administration Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq A socially and environmentally just way to fight climate change MORE — had done so in exchange for positions in a Democratic presidential administration.

Comey and his wife previously donated $2,700 to Klobuchar’s campaign. They were in the same law school class at the University of Chicago.

Trump fired Comey in May 2017 as the bureau investigated Russian interference in the 2016 presidential election, a decision that contributed to special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE’s investigation into the matter.

The Justice Department’s inspector general last year found that Comey violated bureau policies and his employment agreement with his handling of official information while serving as director. According to the inspector general's report, Comey shared unauthorized information about ongoing investigations with a friend, who later gave the information to The New York Times.

Comey has denied that providing the information was a "leak," saying he believed the information was unclassified.

Trump continues to frequently tweet about Comey, who responded last week with a Mariah Carey gif that reads, "Why are you so obsessed with me?"