It wasn't all that long ago that the prospect of a contested Democratic convention was every savvy Washingtonian's favorite topic of conversation. Traditional political journalists, who are habitually bored and irritated by the smoothly stage-managed and substantively anticlimactic nature of modern conventions, seem to envy the days when their forerunners like H. L. Mencken witnessed the excitement of a political party actually resolving its nomination contest in a blur of stem-winding speeches, repeated roll-call votes, and dark-horse bandwagons. But their predictable musings, usually accompanied by ill-disguised hope, at the beginning of every nomination season that the imminent primary race could easily produce such a thrilling grand finale received reinforcement this year from the ranks of the cutting-edge quantitative analysts. According to the FiveThirtyEight forecasting model, the probability of no single Democratic candidate receiving a majority of delegates spiked after this year's Iowa caucus, briefly rising well over the 50 percent mark prior to Super Tuesday.
Of course, that all seems rather quaint now. Joe Biden's remarkable resurgence, beginning with his modest second-place finish in the Nevada caucus and picking up rocket fuel the following week in South Carolina, extended through another week's worth of elections this Tuesday night. Barely a month after his damaging losses in Iowa and New Hampshire seemed to bring his campaign to the edge of a cliff, Biden is poised to assume the mantle of presumptive Democratic nominee.
What's more, the procedural mechanism that previously made a contested Democratic convention seem so very possible—the party's requirement that delegates must be allocated in proportion to the popular vote in individual states and congressional districts—is the same thing that will now help Biden's campaign make the case that the race is effectively over. At the beginning of the primary sequence, with so many active candidates dividing voter support, it's only natural to suppose that no single contender may be able to attract an outright national majority of delegates. Republican candidates can quickly amass a strong advantage even without a popular majority by placing first in multiple states that award delegates in a winner-take-all fashion, but national party rules close off that path for Democrats.
At the current stage of the nomination sequence, however, proportional allocation becomes a Democratic front-runner's best friend. Biden's lead in the delegate count, though it may not appear numerically lopsided at first glance, has in fact become sufficiently large that only a series of crushing defeats in state after state would seriously endanger it. A Republican candidate in Sanders's position could conceivably ride victories in multiple winner-take-all states to make up ground quickly in the back half of the primary calendar, but the Democratic Party's proportionality requirement dramatically blunts the impact of upsets late in the process. Both Hillary Clinton in 2008 and Bernie Sanders in 2016 notched some notable wins in populous states during the final phases of the primary season, but they had both already fallen far enough behind their opponents that anything short of repeated landslides wasn't going to throw the final outcome into doubt.
And so, like in many other years, the 2020 presidential nomination system has quickly transformed apparent chaos and uncertainty into order and predictability. There are still more states to vote, more questions to resolve, and more strategic choices ahead for both Biden and Sanders. But unless a truly extraordinary disruption occurs in the race, the process has now foreclosed any other outcome than the one that now stands before us.