Joe Biden is tanned, rested, and ready.

The former vice president is aggressively campaigning for Democrats in this year's elections, and none too displeased that people keep asking him whether he'll run for president. As recently as December he said, "I may very well do it," and whenever the question of Democrats' appeal to those magical white working-class voters comes up, someone inevitably says that what they need is a candidate like Uncle Joe (Did you know he's from Scranton? Well he is!). Which leads many of the liberals I know to groan in agony.

But they shouldn't worry. Biden, who will be 77 when the next Iowa caucuses roll around, obviously never stopped yearning to be president. He should run if he wants. But if he does, he'll almost certainly fail to get the Democratic nomination, and the reasons why tell us a good bit about 2020 and presidential campaigns in general.

I should note that in the past I've praised Biden's performance as vice president. But few things challenge a politician quite like the presidential primaries. Their persuasiveness, their charm, their stamina, their strategic acumen, their fundraising skills, their ability to avoid mistakes, all are tested in that extraordinary slog. Joe Biden stepped up to that test — and fell on his face. Twice.

Let's review a little Biden history. In 1987, the eloquent, energetic young senator (he was 45 at the time) mounted his first run for president, and it didn't go well. At a debate at the Iowa State Fair, Biden gave an inspiring closing statement about his hardy and noble ancestors who worked in the coal mines for 12 hours and then came up to play football, yet didn't have the chance to go to college like he did. It turned out that the passage was lifted almost word-for-word from a speech by British Labor Party leader Neil Kinnock — though Kinnock had said his coal mining forebears spent only eight hours a day in the mines, and the football he referred to was one played with a round ball. Other plagiarism instances surfaced, and in September 1987, Biden withdrew from the race, saying he was "angry at myself," but also that "I am no less frustrated for the environment of presidential politics that makes it so difficult to let the American people measure the whole Joe Biden and not just misstatements I have made."

Twenty years later, a more seasoned Biden gave it another shot. The response of Democratic voters was underwhelming, to say the least. In 2008 he placed fifth in the Iowa caucuses, garnering less than 1 percent of the delegates, then withdrew from the race the next day.

Which makes you wonder why anyone would think he'd be a particularly formidable candidate in 2020. Yes, many Democrats are concerned about their showing with white voters, and Biden is indeed a white guy. But if that's all it took, then Barack Obama would never have been president. That's not to mention his age, a perfectly legitimate concern (he'd be 86 at the end of a second presidential term), the fact that he's an unstoppable gaffe machine, or the fact that while I have no idea whether Biden has ever sexually harassed anyone, to call him "handsy" would be a huge understatement.

So Democrats who don't like the idea of a Biden candidacy have little to fear from his entry into the 2020 race. Which is a reminder that you don't have to worry that some candidate you don't like is going to ruin everything for everyone else.

You might argue that in certain circumstances, one candidate bigfoots the race, driving other potentially more worthy contenders from the field, like Al Gore did in 2000 or Hillary Clinton did in 2016. But that's only partially true. Were others scared off by those "presumptive" nominees? Sure. But they didn't have to be. Bill Bradley ran in 2000, and Bernie Sanders ran in 2016 (as did Martin O'Malley and Lincoln Chafee, you'll recall). They gave it their best shot, primary voters had an ample opportunity to look them up and down, and those voters decided to go with the frontrunner.

But more to the point, 2020 is going to be the most wide-open Democratic nominating contest in pretty much forever. There is no frontrunner, because there will probably be a dozen potentially strong candidates. (Though Sanders will lead in early polls, he probably won't be able to repeat his strong showing last time, when his campaign became a cause particularly among the young mostly because he was the only real option to Clinton. Bernie '16 was a unique phenomenon; when he's one of a dozen candidates, he won't be nearly as compelling.)

I'm pretty sure that neither Kirsten Gillibrand, Cory Booker, Kamala Harris, nor any of the other 500 or so Democrats contemplating running in 2020 is going to be scared away by the presence of Joe Biden, or anyone else for that matter. When the 2020 campaign begins (which will happen the day after Election Day 2018, just to warn you), Democrats will have something extraordinary: an enormous collection of potentially interesting candidates to choose from. Some will turn out to be less attractive than people thought, some will turn out to be even more interesting, and in the end the best one will prevail.

And if you're a Democrat, your best bet is to support the person you like the most — not the one you think will appeal to some portion of the electorate a pundit told you was important, or who you think matches up better against President Trump in some critical way. Just pick the one you most want to see as president. When voters do that, it's much more likely to turn out well.

For some Democrats, that candidate will be Joe Biden. But probably not that many.