There are plenty of primaries to go over the next couple of months, and November is still a long way off. But on the night that Democrats cast their primary ballots in six states across the Midwest, South, and Northwest — including the important state of Michigan, which played such a significant role four years ago — it became abundantly clear that former vice president Joe Biden is bound to become the party's choice to take on President Donald Trump on Election Day.

March 10, 2020 is the day that Biden became all but unbeatable.

This isn't because Biden will come out of the day's six contests with an insurmountable delegate lead over Vermont Sen. Bernie Sanders. It's because today's wins will likely be followed by Biden beating Sanders in Florida next Tuesday by around 40 points, and in Illinois, Ohio, and Arizona by double digits on the same day. And this will likely be followed by Biden victories in Georgia, New York, Pennsylvania, Maryland, Connecticut, Delaware, and numerous other delegate-rich states across the country, allowing him to lock down the nomination.

We know that this is the overwhelmingly likely outcome not only because that's what the polls are telling us. We also know it because the results on Tuesday night confirm what's been clear since Super Tuesday, which is that Biden is doing better than Hillary Clinton did the last time around, and Sanders is doing significantly worse.

The Mississippi results are consistent with both Biden's showing in South Carolina on Feb. 29 and Clinton's in Mississippi four years ago: The more centrist, establishment candidate wins with roughly 80 percent of the vote, while the insurgent democratic socialist finishes in the mid-teens, largely because of the ideologically moderate black vote in the South. (Biden's record of serving as Barack Obama's wingman for eight years certainly doesn't hurt him with these voters, but the results this time are remarkably consistent to what they were in 2016.)

What was a very serious Sanders weakness four years ago remains one today. But to it has been added at least one more: He is no longer running against Hillary Clinton.

It may be unfair to Biden to put it that way, but it's hard to look at the results in Michigan, in particular, without wondering just how much of the 2016 results in that state, both in the primaries and in the general election, were a function of the unique dislike the former first lady and secretary of state was capable of generating among voters.

Consider: Sanders shocked the political world four years ago by defying the polls and narrowly beating Clinton in the Michigan primary. On Tuesday night, he appears to be on track to lose to Biden by roughly 13 percentage points. Sanders won Kalamazoo County by 22 points in 2016. This time he narrowly lost it to Biden. In Washtenaw County, home of Ann Arbor and the University of Michigan, Sanders beat Clinton 55 to 43 percent. Against Biden, Sanders has lost it 48 to 46 percent. Once all the votes are counted in Michigan, it's likely that we'll learn that Sanders underperformed his 2016 vote percentages by an average of double digits.

The results in Missouri were even starker. In 2016, Sanders lost the state to Clinton in a photo-finish, with the final results showing the candidates separated by just 0.2 percent. This time Biden looks on track to win it by a massive 25 points. When a candidate runs for president in back-to-back cycles and hemorrhages that many votes, it's an undeniable sign of softening.

Even out West, where Sanders has enjoyed his greatest strength, things look bleak. In 2016, Sanders bested Clinton in the Washington State caucuses 72 to 27 percent. On Tuesday night, Sanders and Biden were neck-and-neck, effectively tied, with two-thirds of the primary votes counted. Likewise, in Idaho, Sanders' 56-point blowout in the state's caucuses four years ago had become a narrow lead for Biden with over half the vote in. Even if Sanders claws his way back to take both states, the contrast to 2016 will remain stark.

The Sanders campaign is floundering and deflating. Which means that the Biden campaign, facing no other viable opponents, has now become virtually unstoppable in its march to the Democratic nomination. It remains to be seen whether the former vice president will prove more capable than the 2016 nominee of beating Donald Trump. But the results on Tuesday night give Democrats reason to suspect that he might.

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