By late March, nearly 60 percent of pledged delegates will be elected. With a large field, this arithmetic makes it vanishingly unlikely that a nominee will be chosen on the first ballot.

Front-runners Bernie Sanders and Pete Buttigieg won Iowa and New Hampshire with barely 26 percent of the vote, a record low. Nevada portends more of the same—a fragmented field, a weak winner.

At least six candidates will likely be alive through Super Tuesday (March 3) and quite possibly beyond—Sanders, Buttigieg, Klobuchar, Bloomberg, Biden, and Warren. This fragmentation well into the primary season is unprecedented. None of them will win more than a third of the total delegates.

Therefore, to be nominated on the first ballot, a breakout candidate would need to win more than 60 percent of the delegates in the remaining primaries after March. No way.

The last convention that went beyond the first ballot was in 1952. Illinois Governor Adlai Stevenson came in third on the first ballot, and it took three ballots for him to win.

What would a brokered convention look like in 2020? To open, we will have the anybody-but-Bernie faction facing the anybody-but-Bloomberg faction.

There will be a frantic quest for a unity candidate. That could be Warren if she can break out of single digits and revive her campaign. It’s hard to imagine any other current candidate being even grudgingly acceptable to Sanders forces, many of whom might bolt and even mount a write-in campaign.

Given Bloomberg’s well-earned troubles with blacks, women, and progressives, it’s also hard to imagine Bloomberg emerging as the unity candidate no matter how many billions he spends. One can even imagine the convention going outside the current field to Ohio Senator Sherrod Brown.

This will be a mess, with a lot of activists feeling betrayed. One can only hope that Democrats will realize the stakes, put aside grievances from a protracted and often ugly campaign, and get behind their nominee.