The answer is that under the Democrats’ new rules, that could prove mathematically challenging. By March 3, nearly 40 percent of the pledged delegates will have been chosen. Those delegates will be allocated proportionately to the vote in each state and district, among candidates who earned at least 15 percent of the statewide vote, and at least 15 percent within each district. If as many as five candidates have managed to clear the threshold in several different states, it’s not implausible that no candidate would have won more than a third of those delegates.
In that eventuality, the delegate leader would need to earn upwards of 60 percent of the remaining delegates to get a majority. That’s a daunting number: It would require the leader to win very nearly every remaining state, including Bloomberg’s New York, Biden’s Pennsylvania, and states like Michigan and Wisconsin that have proved fertile ground for Sanders in the past. Finally, with superdelegates no longer eligible to vote on the first ballot, if there’s no majority, then we’ve got a contested convention.
It’s unclear whether establishment Republicans in 2016 could have closed ranks to stop Trump; there may have been no pro-establishment majority at all, but rather an anti-establishment majority divided between Cruz and Trump. But under the Democrats’ rules, they wouldn’t have needed to; a divided field of candidates all earning delegates would have denied any candidate a majority.