Joe Biden is marching to the Democratic presidential nomination.

The former vice president handily defeated Bernie Sanders on Tuesday in Michigan's primary -- halting the Vermont senator's hopes of a comeback in the state where he'd stunned Hillary Clinton four years ago.

Biden also notched massive wins in Idaho, Mississippi and Missouri. Sanders won in North Dakota. Washington hadn't been called yet, but as of Wednesday morning, Biden was in a tight race there with Sanders, another state Sanders needed to win.

Tuesday marked a clear turning point in the Democratic race. Biden is building a powerful coalition of African Americans, suburbanites and rural white voters who previously backed Sanders, while Sanders is failing to produce the electorate-changing turnout of young voters that he's promised. Democratic figures, from one-time 2020 candidate Andrew Yang to the party's biggest super PAC, Priorities USA, lined up behind Biden after his Michigan win.

Biden and Sanders are scheduled to debate Sunday night in Arizona. But Sanders is entering a brutal stretch, with primaries next week in Arizona, Florida, Illinois and Ohio -- all states he lost in 2016. There's also the reality that coronavirus could crowd Sanders out of national headlines and make it impossible for him to leverage something that separates him from Biden: his ability to turn out massive crowds at rallies. It all makes a comeback even more difficult.

Here are five takeaways from Tuesday's contests:

Biden begins his pivot

Speaking at the National Constitution Center in Philadelphia, Biden delivered a message of Democratic unity, extending an olive branch to Sanders and his supporters -- almost as if the Vermont senator had already exited the race.

"I want to thank Bernie Sanders and his supporters for their tireless energy and their passion," Biden said. He echoed a common Sanders line on health care, touted their "common goal" and said they would work together to defeat Trump.

It capped a 10-day stretch in which a largely counted out Biden completed one of the most sudden and dramatic reversals of fortune in modern political history. It started with his massive win in South Carolina's primary, built with his wins in 10 of the 15 Super Tuesday contests and was capped off with a victory over Sanders in Michigan, a crucial general election battleground.

Biden has shown some vulnerabilities -- most urgently, his lack of support from young voters. But he is also outperforming Clinton in the primary race with suburban and white working-class voters, giving Democrats a clear potential path to victory in November.

Biden made clear Tuesday night he is eager to turn his attention to a general election match-up with President Donald Trump.

Sanders, meanwhile, countered Biden's unity message with nothing at all. At home in Burlington, Vermont, he did not speak Tuesday night.

Sanders has a decision to make

Michigan delivered Sanders his best night of the 2016 primary, reviving his campaign as Clinton threatened to run away with the nomination. In 2020, the state might have done the opposite -- beating down his campaign and opening the path for Biden to break clear in the delegate race.

Sanders' loss in Michigan is both a mathematical and psychological wound. For years now, Sanders and his supporters have pointed to the state, and his success there, as evidence that he would have defeated Trump in 2016 -- and would if given the chance now. The Vermont senator didn't run away from the stakes; instead, he ran toward them, canceling a trip to Mississippi in order spend more time in Michigan, which he repeatedly called "the most important state" voting on Tuesday.

But the added time did not add up to a better-than-expected result. Biden, like he did in Missouri and Mississippi, grew his support and delegate lead. And just like after the former vice president won in South Carolina, he also got a boost from some of the party's biggest names, who argued that the race is over and Sanders should acknowledge as much.

The Sanders campaign has rejected any suggestion that he might consider dropping out any time soon -- and certainly not before Sunday night's debate -- but those hopes could soon be replaced by a colder calculus.

"He'll debate," a Sanders aide said of his upcoming showdown with Biden in Arizona on Sunday night. The aide wouldn't go any further.