Biden summoned high turnout from precisely the diverse constituencies of African-Americans, suburbanites, working-class and older voters that another aging pol more at home with coalition politics than movement politics—House Speaker Nancy Pelosi—marshalled to re-take the House in 2018.

In the near-term, Biden’s achievement indicated that Sanders has no convincing path to defeating this coalition with young people or previous non-voters. The only formula for his revival would involve Sanders somehow managing to encroach on support Biden won so handily from these groups. If not, it’s shovel time, no matter how long the nomination contest slogs on (which likely will be quite a while).

For the general election, the implications of Tuesday are equally urgent for Trump. Voter turnout in the primaries was up from 2016 in almost every state—in Virginia, for instance, turnout increased by more than two-thirds. The overwhelming evidence is that it is Trump, not any Democrat, who is stimulating this surge. Increased energy on the Democratic side, in the likely event this holds through the fall, means Trump must also stimulate new voters or it is shovel-time for him, too.

Perhaps most profoundly, Tuesday night represented history reasserting itself. It was a signal that not all the old ways of thinking about national politics are defunct in an age of disruption.

So much of the Trump era has been so bizarre—from the circumstances of his 2016 victory to payoffs to a porn star to the surrender and servility of former Republican critics—that it can’t be understood with reference to precedent or familiar norms. The Trump era has been a séance with Henry Ford, who famously said, “History is more or less bunk.”

Biden’s victory, contrast, can be understood through a historical prism—indeed it doesn’t really make much sense through any other prism. The old saw that Democrats fall in love while Republicans fall in line has not usually been true. In most nomination contests for the past 40 years—Jimmy Carter in 1980, Walter Mondale in 1984, Bill Clinton in 1992, John Kerry in 2004, Hillary Clinton in 2016—the party has ultimately coalesced over the more consensus-oriented politician in the spring after a flirtation with more flamboyant or purely ideological insurgents.

There’s nothing mystical about these migratory patterns. It reflects that majority power in the Democratic Party resides in familiar places among familiar constituencies whose habits and allegiances stretch back decades. What was notable on Super Tuesday was the suddenness and velocity with which this customary migration took place, as well as how it benefited even a candidate whose political infirmities most of the past year have been on such glaring display.

The fact that history is reasserting itself does not mean that the next several months are about to become routine or easily predictable. To the contrary, most of what we in the POLITICO newsroom are observing suggests that events are going to remain very interesting.

Some other Super Tuesday observations:

Movement politicians create counter-movements

Journalists instinctually love to explain outcomes through dramatic moments: the climactic showdown, the secret strategy, the behind-the-scenes story.

After a cup of coffee or two, however, most of the narrative reconstructions about Biden’s comeback seem a bit facile—not wrong, just insufficient. His revival is more indicative of something deep and important going on in the electorate precisely because it does not have a plausible precipitating event.

Yes, South Carolina’s Jim Clyburn is a respected African-American leader, and has been for decades. But there are not previous examples of him directing huge swaths of voters in his state or across the South merely on his say-so. His endorsement likely was powerful not because so many of his loyalists were waiting to be told what to do by him but because he understood what many of his loyalists were already feeling. (Biden was ahead in South Carolina's absenteee voting before Clyburn’s endorsement.)

Likewise, Biden’s team no doubt needed an infusion of energy from a talented political veteran like Anita Dunn. But it’s hard to conceive that any internal changes had much to do with Tuesday’s Biden wave, which was not accompanied by any big change in messaging or spending. Biden’s most recent debate performance and his victory speech after South Carolina were better than some previous outings but were hardly Churchillian.

The more credible explanation was that these things were like well-timed sparks in a dry forest.

Specifically, while Sanders is a movement politician, the socialist who has never formally become a Democrat is clearly also creating a counter-movement within the party. The number of late-deciding voters, as reflected in exit surveys, suggests that many Democrats desperately want to reconvene the 2018 mid-term coalition to defeat Trump and fear Sanders is not the right person to do that. The counter-movement, based on latest evidence, is larger than the movement itself.

This is also the peril for Trump, the greatest movement politician of the past couple generations. Typically, movements compensate for smaller raw numbers with the greater passion of adherents. In this case, though, it’s likely he has inspired equal or greater passion among the opposition.

Not all the history is encouraging for Biden

Long marches to the nomination often don’t bode well for general election prospects. This is true historically, as in Jimmy Carter’s loss to Ronald Reagan in 1980 after a bitter nomination fight against Ted Kennedy. And it’s true recently, as in Hillary Clinton’s loss to Trump after an extended and sullen contest against Sanders. A large survey released in 2017 by the Cooperative Congressional Election Study found that 12 percent of Sanders voters ultimately backed Trump. Others did not vote at all.

The other relevant history concerns Biden himself. If he were an articulate and even-performing politician it is possible he would have taken command of the race months ago. The candidate who often meandered in debates, who has ample baggage after 50 years in politics, who never won a state in two previous presidential runs, is the same candidate who today has the aura of a winner. We can be sure there will be many challenges to that aura from both Sanders and Trump in the days ahead.

Democrats remain in a highly fluid state

Just as Trump is almost a cartoon version of a political disrupter, Biden can look like a cartoon version of a return to conventionality.

Don’t forget that even the most moderate Democrats in the 2020 race, Biden among them, backed ideas on expanding health care and bringing business to heel that went well beyond what a progressive like Barack Obama supported in 2008.

It is improbable that Biden is in the process of marshalling an ideological mandate. More likely: Super Tuesday voters eager above all to beat Trump regarded Sanders’ democratic socialism with its high expense and uncertain popular appeal as a bridge too far.

But Biden is perfectly credible as an ideological placeholder until the party’s reappraisal for a new generation of voters is more mature. That reappraisal is coming in any event. An analysis by a center on youth voting at Tufts University’s Tisch College showed Sanders winning the under-30 vote in all nine states where data was immediately available. In Minnesota, despite Biden’s late-surging victory, one in five voters was under 30, a percentage tied with Massachusetts for highest on Super Tuesday. Despite Biden’s 30-point win in Virginia, Sanders still won 55 percent of younger voters.

The human dimension matters

It is notable how many politicians backing Biden cited his personal decency and kindness. Historically, these have not been major prerequisites for the presidency. To the contrary, at times (as in the case of Richard Nixon and Trump) voters have seemed to reward a certain ruthlessness, as evidence of necessary strength in the presidency. It seems likely Trump’s pattern of insults and conflict in office have many voters placing a premium on opposite traits.

Sanders, whose strengths are consistency and passion, often seems to view politics as a clash of interests which casts “the people” as more of an abstraction, rather than connecting with or projecting empathy toward individual people with their flesh-and-blood problems.

This dynamic could be an important factor during the balance of March. Based on Tuesday, Biden looks well-positioned for contests in Louisiana, Mississippi, Illinois and Florida. More competitive—and therefore an opportunity for Sanders to hit the brakes on the trajectory of the race or for Biden to become de facto nominee—are Arizona, Michigan, and Ohio.