It’s pretty generally recognized that four 2020 Democratic presidential candidates have separated themselves from the rest of the field. But not many observers are teasing out the implications if it continues, as I tried to do this week at New York:

[L]ess than a year before Democrats meet in Milwaukee to nominate a presidential candidate, the field’s two old white men have lost a significant amount of support, while two women (Elizabeth Warren and Kamala Harris) have gained significant strength. While everyone understands that Warren and Harris represent a threat to Biden and Sanders, it’s underappreciated how much all four candidates are now separated from the rest of the field.

Using the RealClearPolitics national polling averages as a yardstick, as recently as two months ago, Biden was at 38 percent and Sanders at 19 percent, with Warren, Harris, and Buttigieg clustered in the high single digits; O’Rourke and Booker were a few points behind them; and everyone else was struggling for oxygen. Now Biden (28 percent), Sanders (15 percent), Warren (ditto), and Harris (13 percent) are more closely bunched, with Buttigieg the next in sight at 5 percent. After a boffo second quarter in fundraising, Mayor Pete may have the resources to lift himself from the madding crowd the way Warren and Harris have done. And some other current bottom-feeder could rocket into contention with a big-time performance in the July 30 and 31 debates in Detroit (after that, the heightened requirements for participation in two rounds of autumn debates are likely to serve as an abattoir for struggling candidacies).

And as noted, there are scenarios under which each of these four candidates could put it all away early. Most obviously, despite his recent loss of support nationally, Biden remains in the lead in all four of the early states that vote in February. If he wins them all, he’d be extremely hard to stop. Sanders has one of the more consistent bases of support in the key early states, is showing signs of addressing his minority-voting weakness from 2016, and has plenty of money, so he could plausibly win Iowa and New Hampshire and roar into Super Tuesday with a head of steam. Warren has what is generally conceded to be the best Iowa organization, is rising rapidly in New Hampshire, and can compete with both Sanders and Biden in harvesting good will among a national constituency of admirers. And Harris, building on her first-debate success, has a very plausible Obama-esque strategy of wrecking Biden in South Carolina among the black voters he heavily relies upon, and then forging into front-runner status with a big win in her native California just a few days later.

But if all of these candidates fall just a bit short of their most ambitious goals, and fail to land the knockout punch when they need it, then we could be looking at a truly protracted battle in which no one rival has an indomitable advantage. That does not necessarily mean a contested convention would occur: candidates could try to achieve some breakthrough via unconventional coalitions, alliances among themselves, or early running-mate announcements (tried unsuccessfully by Republicans Ronald Reagan in 1976 and Ted Cruz in 2016, but still worth considering). Democrats do not strictly require pledged delegates to stick with their original candidates (particularly if that candidate has withdrawn), so things could change before delegates arrive in Milwaukee. And then, yes, a gridlocked convention could turn to suddenly re-enfranchised superdelegates, all 764 of them, to help make a decision after the first ballot ends.

If nobody’s made a big move by early March, it’s time to start thinking seriously about these wild convention scenarios — and about which candidate might best unify the Donkey Party. By this time next year, the fear of letting Trump win again will be so palpable that you will be able to weigh it on scales and grill it up for an anxious meal.