DETROIT (AP) — Presidential politics move fast. What we're watching heading into a new week on the 2020 campaign:

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Days to next set of primaries (Idaho, Michigan, Mississippi, Missouri, North Dakota, Washington) : 1

Days to general election: 249

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THE NARRATIVE

The earth has shifted over the last seven days. The Democrats’ 2020 primary has suddenly become a two-person race in which Joe Biden has a distinct advantage over Bernie Sanders. It’s difficult to exaggerate the speed with which things have changed. Last weekend there were five major candidates still in the primary fight, and Sanders was threatening to build an insurmountable delegate lead. But in the span of 72 hours, two leading moderates dropped out and the party’s establishment wing sprinted into Biden’s camp. The former vice president used the extraordinary rush of momentum to seize a delegate advantage on Super Tuesday. And with Sanders struggling to unify the progressive wing behind him ( Elizabeth Warren is out but has refused to endorse), he enters another multistate primary test on Tuesday facing the prospect that Biden could soon build an insurmountable delegate lead.

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THE BIG QUESTIONS

Can Bernie get back on track in Michigan?

As we learned last week, it’s a mistake to focus too much on one state. After all, Sanders won Super Tuesday’s biggest delegate prize, California, and still finished the day with fewer delegates than Biden. With that warning, Michigan deserves your attention this week. The Midwestern state offers the largest trove of delegates on Tuesday and, almost as importantly, serves as a huge symbolic test of Sanders’ remaining political strength. Michigan helped rescue his candidacy four years ago, and it sits as one of three key battlegrounds Democrats desperately need to win in November. Going in this time, Sanders’ team had been supremely confident about his standing with the state and its large working-class population — at least until last week’s shakeup. Sanders knows he will not win them all, but he can’t afford to lose this one.

How does Biden handle front-runner status this time?

Biden has plenty of experience as a front-runner. And he hasn't always fared so well under the bright lights that go with it. After nearly being forced from the race last month following a dreadful start, the 77-year-old gaffe-prone Democrat gets another chance to prove he belongs on top. He will benefit from a lack of establishment alternatives should he stumble. He'll also benefit from the new phase of the race, which has essentially become a series of national contests where voters won't get to see the candidates as closely as they did in Iowa, New Hampshire, Nevada and South Carolina. Still, make no mistake: Biden will face a new wave of fire from the right and the left this week as he seeks to tighten his grip on the Democrats' presidential nomination.

Will Warren help unite progressives?

Warren's silence has been notable. As a crush of establishment Democrats raced to line up behind Biden, the fiery progressive senator has refused to endorse her closest ideological ally, Sanders. There was obvious tension between Warren and Sanders during the primary, yet the same could be said of the many moderate candidates who are now standing behind Biden. Every day Warren sits on the sidelines hurts Sanders. He desperately needs a united progressive wing to defeat Biden, yet key pieces of Warren's coalition are holding back until she makes her move. This is the kind of decision that could have dramatic short- and long-term consequences for the progressive movement.

How will a two-man debate change things?

There have never been fewer than six Democrats on the debate stage at one time in the 2020 primary season. Next Sunday in Arizona, there will be just two. And in case you missed it, neither is a woman or a person of color or under the age of 77. There are clear ideological differences, of course. Despite Biden and Sanders' superficial similarities, the silver-haired septuagenarians will face off representing starkly different views of the future of the Democratic Party and the nation. Sanders thinks he'll benefit from having more time to delve into issues of substance. And with more than four decades in Washington, Biden has a long record to answer for. There will be an unmistakably new dynamic on stage that may give voters their best glimpse so far of how each candidate would perform in a one-on-one debate with President Donald Trump this fall.

Can Trump handle the coronavirus outbreak?

The Republican president is facing the greatest leadership test of his first term. And, so far, Trump is struggling to grasp basic facts about the rapidly escalating coronavirus threat, which has infected hundreds of Americans across 34 states and counting. That's even as he and his administration publicly declared last week that the virus was contained. And beyond public health, the economic fallout could be disastrous. Wall Street just suffered its worst week in more than a decade, and travel companies are bracing for massive losses. The general election is just eight months away. Trump needs to show he can lead the country through this growing crisis or face the consequences in November.

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THE FINAL THOUGHT

There's no need to panic, but the coronavirus threatens to shape American life in 2020 far more than some expected. Public officials are planning for the likelihood that professional sports will be played in empty arenas. Airlines have begun canceling flights. And schools are being closed. It's fair to wonder whether political events may be curtailed sooner rather than later. Even if the death toll remains relatively low, this epidemic may affect all of us in some way before it's over.

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2020 Watch runs every Monday and provides a look at the week ahead in the 2020 election.

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Follow Peoples at https://twitter.com/sppeoples.

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Catch up on the 2020 election campaign with AP experts on our weekly politics podcast, “Ground Game.”