Sen. Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE (I-Vt.) slipped further behind former Vice President Joe Biden Joe BidenCast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response Biden tells CNN town hall that he has benefited from white privilege MORE in the race for the Democratic nomination for president on Tuesday, all but certainly closing his path to a first-ballot victory at the party's convention in Milwaukee.

Early results showed Biden winning Mississippi, Missouri and, crucially, Michigan, a state that revived Sanders's long-shot bid against Hillary Clinton Hillary Diane Rodham ClintonHillicon Valley: FBI chief says Russia is trying to interfere in election to undermine Biden | Treasury Dept. sanctions Iranian government-backed hackers The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters FBI chief says Russia is trying to interfere in election to undermine Biden MORE in 2016.

Biden led in Idaho, and the two front-running candidates were neck and neck in Washington, though The Associated Press had not yet called those races. Sanders led a firehouse caucus in North Dakota, the smallest state on the docket Tuesday.

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Biden's wins in the biggest states up for grabs on Tuesday represented the latest blow to a Sanders campaign that had counted on a fractured Democratic field lasting late into the primary season.

Instead, moderates and mainstream liberals began to coalesce around Biden after the South Carolina primary 10 days ago, when Biden's decisive win convinced both 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.) to exit the race ahead of Super Tuesday.

Buttigieg and Klobuchar endorsed Biden, who went on to sweep 10 of 14 contests held on Super Tuesday. In the days that followed, he has further consolidated the once-divided Democratic field, winning endorsements from Sens. Kamala Harris Kamala HarrisScott Walker helping to prep Pence for debate against Harris: report California family frustrated that governor, Harris used fire-damaged property for 'photo opportunity' Moderna releases coronavirus vaccine trial plan as enrollment pushes toward 30,000 MORE (D-Calif.) and Cory Booker Cory Anthony BookerDHS opens probe into allegations at Georgia ICE facility Democratic lawmakers call for an investigation into allegations of medical neglect at Georgia ICE facility Black Voters Matter Fund deploying voter outreach caravans in 12 states to drive turnout MORE (D-N.J.). On Tuesday, after it became clear Biden was headed for victory, entrepreneur Andrew Yang Andrew YangDoctor who allegedly assaulted Evelyn Yang arrested on federal charges The Hill's Campaign Report: Biden weighs in on police shootings | Who's moderating the debates | Trump trails in post-convention polls Buttigieg launches his own podcast MORE, a Sanders supporter in 2016, said he would back Biden.

In a victory speech Tuesday, Biden seemed to begin the process of uniting a fractured party around his candidacy with sympathetic words toward Sanders supporters.

"I want to thank Bernie Sanders and his supporters for their tireless energy and their passion. We share a common goal, and together we'll defeat Donald Trump," Biden said at a small gathering in Philadelphia.

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Sanders did not address the media or supporters on Tuesday.

Sanders has cast himself as the candidate best able to turn out a swath of new voters necessary to beat President Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE in November, but his campaign has shown little ability to add to the coalition it built in 2016. Michigan is the fourth state Sanders has lost this year after winning it in 2016, along with Oklahoma, Minnesota and Maine.

Sanders also won caucuses in Washington and Idaho in 2016 — both states that have since transitioned their nominating contests to primaries.

He has won California, though his margins over Biden have shrunk to about 7 percentage points with 2.4 million ballots left to count, and Nevada, where Clinton narrowly edged him in 2016.

There are few signs that Sanders is adding a huge number of new voters to the Democratic electorate. Most states that have voted so far have shown no substantial growth among younger voters. On Tuesday, only 17 percent of Michigan voters said they were casting their first ballot in a Democratic primary — and among those voters, Sanders led Biden by only a 52 percent to 44 percent margin, according to early exit polls.

Instead, the Democratic electorate seems to have consolidated around Biden as the answer to the most pressing question they face: Who is best equipped to beat Trump in November?

In Michigan, 57 percent of Democratic primary voters said their party should nominate someone who can beat Trump in November, and Biden beat Sanders among those voters by an almost 2-to-1 margin. In Washington, almost 7 in 10 Democrats wanted their party to pick a candidate who could beat Trump over a candidate who agrees with them on most issues, and Biden again took those voters by a more than 2-to-1 margin, exit polls showed.

Even before the final delegates have been allocated from Super Tuesday, the results a week later showed Biden increasing his lead in the race for delegates over Sanders. Biden was on pace to claim 28 of Mississippi's 31 pledged delegates, 38 of Missouri's 59 pledged delegates and a clear majority in each of Michigan's 14 congressional districts.

The early results put Biden 150 delegates ahead of Sanders and more than 40 percent of the way to the outright majority of delegates he would need to win the Democratic nomination outright. To climb back, projections showed Sanders would have to win more than 56 percent of the remaining delegates up for grabs before the Milwaukee convention, a herculean task even before voters started breaking heavily toward Biden.

What's worse for Sanders is that the calendar in the immediate future becomes only more difficult for him. The next round of Tuesday contests feature two contests that are likely to break for Biden, in Arizona and Florida. Polls in both of those states show Biden easily lapping Sanders in support.

That leaves Sanders banking on next Tuesday's other two contests, in Illinois and Ohio. Prominent elected officials in both states have flocked to Biden in recent days, a sign that the party continues to coalesce around its newfound front-runner.

Both Biden and Sanders had planned to stump in Cleveland on Tuesday, after the polls closed in other states, but both campaigns canceled their rallies after warnings about spreading the coronavirus.