When Joe Biden won the South Carolina primary on Saturday with nearly 50 percent of the vote, it was his first outright victory in three attempts at securing the Democratic presidential nomination. It was also the beginning of what looks increasingly like an attempt by the party’s establishment to designate an official moderate challenger to Bernie Sanders, who is leading the polls in the delegate-rich states of California and Texas ahead of this year’s Super Tuesday contests.

Amy Klobuchar announced on Monday afternoon that she was dropping out and urging her supporters to get behind the former vice president; her announcement was followed quickly by the news that Pete Buttigieg, who ended his campaign on Sunday night, would also be endorsing Biden. Even Harry Reid, whose relations with the vice president under whom he served as Senate majority leader have been strained, has called upon members of his party to unite behind Biden. We can probably expect more of these endorsements soon, though I suspect Barack Obama will continue to remain officially neutral. Meanwhile, some observers are already predicting that Michael Bloomberg may withdraw from the race if he fails to win any states on Tuesday. His departure would leave Elizabeth Warren (who will also face calls to drop out if she loses in her home state of Massachusetts) the only other candidate in what suddenly looks like a manageable-sized primary race. Otherwise, though, for the 77-year-old Biden this is all but a coronation.

Why did it take this long for establishment Democrats to start winnowing the field? More to the point, why did they end up settling on Biden, whose garbled responses to debate questions and downright bizarre interactions with voters have looked more like evidence of serious cognitive decline than amusingly folksy personality quirks? The second question is easier to answer than the first. For all his obvious flaws, Biden is still the safest choice in this race, the two-time running mate of a popular living former president and someone who is at least acceptable to everyone except hardcore progressives. Unlike other candidates who might have been ideologically acceptable to party leaders — Bloomberg, Buttigieg, Klobuchar — he continues to have an advantage among older black voters, particularly in the South, who still arguably represent the single most reliable segment of the Democratic base.

None of these observations is new. They are arguments that could and indeed have been made for more than a year now. Why has it taken so long for the party to fall in line behind Biden? Among his fellow candidates, the answer is simply vanity, a sense that surely they are entitled to a nomination that Biden could easily have won in 2016. For party bigwigs, I think, there has been and no doubt will continue to be concerns that he lacks the mental and physical stamina to make it all the way through November and beyond. Somewhat more cynically, one can also imagine Democratic leaders believing that the great forced consolidation would be easier to sell to voters if it were delayed as long as possible.

What all of this means for Biden is fairly straightforward. Despite his poor showing in previous contests and his lack of fundraising prowess, the former vice president apparently enjoys the full confidence of his party for the moment.

For Sanders things are somewhat more complicated. He and his campaign have always known that sooner or later the fix would be in. Now that it looks to have arrived he must decide how he is going to respond to the fairly unsubtle attempts by his adopted party’s leadership to strong-arm him out of the nomination. Is he going to begin running a parallel campaign against the DNC itself in an attempt to generate enthusiasm among his own progressive base? Or is he going to grin and bear it in the hope that in exchange for being on his best behavior the establishment will respect what is likely to be at most a plurality of pledged delegates at the convention and not take the nomination away from him? His deference did him no favors four years ago, but in 2016 he was not one of America's most recognizable politicians.

Regardless of what eventually happens, it is amusing to think that despite having begun with the largest and most diverse field of candidates in the history of the Democratic Party, the race for the presidential nomination in 2020 will likely come down to a choice between two near-octogenarian, heterosexual white men.