The hashtag “#WriteInBernie” was the number one trending topic in the United States on Wednesday morning, as supporters of Sen. Bernie Sanders (I-VT) struggled to cope with a stunning string of primary losses after Tuesday.

Before the Feb. 29 primary in South Carolina, just ten days before, Sanders had a sizable lead in the race for the Democratic Party presidential nomination. But a big win for former Vice President Joe Biden in the Palmetto State was followed quickly by a dominating performance on Super Tuesday last week, and important victories in “mini Tuesday” this week. Crucially, Biden won Tuesday in the key state of Michigan, which Sanders won in 2016.

As election returns came in, Sanders supporters consoled themselves, and each other, by speculating that he could still win on absentee ballots, or that there might be enough delegates in remaining states to win the nomination.

Others vented frustration at the speed with which the Democratic Party establishment had come together behind Biden, with nearly every other major presidential candidate backing him, to deny Sanders on the edge of victory.

Many of the posts that included the “#WriteInBernie” hashtag warned Sanders supporters not to defect, as some did in 2016 rather than voting for Hillary Clinton, lest they allow President Donald Trump to win again in 2020.

Any true #BernieWarriors will #WriteinBernie . If you don’t, you stand for injustice — Devan Leos (@TheDevanLeos) March 11, 2020

#WriteinBernie is a hashtag for assholes. Don’t be an asshole. — Palmer Report (@PalmerReport) March 11, 2020

A vote for Biden is a vote against M4A, green new deal, same past centrist era were that gave us Trump, if you are unable to see the circle, you really don't get it and the way politics works… #DemExit #WriteinBernie — ZZZzzz1898 (@jdl28110) March 11, 2020

Some of the frustration reflected the fact that some Sanders voters reject the other candidates, as exit polls suggest:

19% of Sanders voters in Michigan say they will *not* vote for the Democratic nominee regardless of who it is in the election for president this November via @CNN exit polls. — Ryan Struyk (@ryanstruyk) March 11, 2020

President Trump fueled some of the infighting with a tweet blaming Sen. Elizabeth Warren (D-MA) for Sanders’s loss:

Pocahontas, working in conjunction with the Democrat Party, totally destroyed the campaign of Bernie Sanders. If she would have quit 3 days earlier, Sanders would have beaten Biden in a route, it wouldn’t even have been close. They also got two other losers to support Sleepy Joe! — Donald J. Trump (@realDonaldTrump) March 11, 2020

Sanders is still scheduled to debate Biden in Arizona on Sunday, but there is speculation that the debate may be called off. CNN has already canceled the live audience and the spin room over coronavirus fears, and there is intense pressure mounting on Sanders to end his campaign as soon as possible and throw his support to Biden.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News and the host of Breitbart News Sunday on Sirius XM Patriot on Sunday evenings from 7 p.m. to 10 p.m. ET (4 p.m. to 7 p.m. PT). He earned an A.B. in Social Studies and Environmental Science and Public Policy from Harvard College, and a J.D. from Harvard Law School. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.