Imagine what this race might look like if other candidates had not taken a pass, delayed their entrance or dropped out early. South Carolina, the next primary (after Nevada’s caucus on Saturday), would be especially significant. Biden’s once huge lead there is shriveling — yet now there is no obvious alternative, especially for many of the state’s African-American voters.

Landrieu, the former mayor of New Orleans whose soaring speech on Confederate statues gave him a national profile, could have been a strong candidate in South Carolina. If Bloomberg — who’s second among black voters nationwide, according to the Quinnipiac Poll — hadn’t been scared away from South Carolina by Biden, Bloomberg might have made himself the clear moderate front-runner. He also could have reduced the perception that he was taking shortcuts.

Or imagine if Cory Booker or Kamala Harris, instead of quitting the race, had adopted a version of John McCain’s 2008 strategy. Like them, McCain entered the race as a potential front-runner, only to struggle. Far back in the polls and with little money left, he stripped down his campaign to the essentials and kept on running. McCain was making a bet on the unpredictability of politics. He won the nomination.

I’m not saying any one of these outcomes would have been likely this year. I’m saying that the field could have been bigger and stronger than it is and that Democrats shouldn’t have been so bashful.

A candidate doesn’t even need to win the nomination for a long-shot campaign to pay off. Reagan set up his 1980 win by taking on an incumbent president, Gerald Ford, in 1976. Warren might be the front-runner today if she, rather than Sanders, had taken on Hillary Clinton four years ago.

So what does this lesson suggest about the rest of the 2020 campaign?

Don’t jump to premature conclusions — or premature despair, if you consider Trump a threat to democracy. I think that Sanders, for instance, could be a problematic nominee, given his self-identification as a democratic socialist and his stances on fracking, immigration and health insurance. But I also think it’s silly to say he has no chance to beat Trump.

It wasn’t so long ago that people were claiming that the other moderates had no chance to beat Biden.