Former Rep. Beto O'Rourke Beto O'RourkeJimmy Carter says his son smoked pot with Willie Nelson on White House roof O'Rourke endorses Kennedy for Senate: 'A champion for the values we're most proud of' 2020 Democrats do convention Zoom call MORE (D-Texas), who dropped out of the presidential race in November, on Monday 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's 2020 White House bid while appearing alongside him at a campaign rally in Dallas.

The move comes as a host of Democrats work to position Biden as the moderate alternative to Sen. Bernie Sanders Bernie SandersSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Schumer, Sanders call for Senate panel to address election security MORE (I-Vt.), the self-identified democratic socialist who has emerged as the front-runner to win the Democratic nomination.

"Tomorrow, March 3, 2020, I will be casting my ballot for Joe Biden," O'Rourke said on the eve of Super Tuesday. "We need somebody who can beat Donald Trump Donald John TrumpBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Military leaders asked about using heat ray on protesters outside White House: report Powell warns failure to reach COVID-19 deal could 'scar and damage' economy MORE. The man in the White House today poses an existential threat to this country, to our democracy, to free and fair elections. And we need somebody who can beat him. And in Joe Biden we have someone who is the antithesis of Donald Trump."

NEW: Beto O'Rourke: "Tomorrow, March 3, 2020, I will be casting my ballot for Joe Biden." https://t.co/9I5diBxpXk pic.twitter.com/l9qzjUgpj7 — This Week (@ThisWeekABC) March 3, 2020

The remarks from O'Rourke arrived on a night in which Biden earned endorsements from three of his former Democratic primary opponents. 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 and 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.) visited Dallas on Monday and voiced their support for the former vice president after bowing out of the race.

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Their exits came after Biden scored a lopsided victory in a South Carolina primary that has appeared to jolt his once-stalled campaign. The win in the state led to a boost in fundraising and newfound optimism among some in the Democratic Party that he could serve as a viable threat to Sanders's candidacy.

Former Senate Majority Leader Harry Reid Harry Mason ReidSenate Republicans signal openness to working with Biden Mellman: The likely voter sham Bottom line MORE (D-Nev.) and former National Security Adviser Susan Rice were two of several prominent Democratic figures to endorse Biden following the primary win.

O'Rourke, who suspended his campaign last year in part due to fundraising struggles, extolled Biden as someone who can "bring us together and heal us," describing him as "decent, kind, caring, empathetic." He also called Biden the person that could reestablish the "moral authority" of the U.S. both domestically and abroad.

Sanders solidified himself as the front-runner to win the Democratic presidential nomination after victories in Nevada and New Hampshire and a virtual tie with Buttigieg in Iowa. Recent polls have showed him with a large advantage over Biden in some of the key Super Tuesday states, including Texas and California.

UPDATED 10:32 p.m.