From left, former president Bill Clinton, former secretary of state Hillary Clinton, Sen. Tim Kaine (D-Va.) and his wife, Anne Holton, the former Virginia secretary of education. Hillary Clinton delivered her concession speech Wednesday after losing the presidential election to Donald Trump. (Matt McClain/The Washington Post)

When she dropped out of the Democratic presidential race in 2008, Hillary Clinton uttered these now-famous words: “Although we weren’t able to shatter that highest, hardest glass ceiling this time, thanks to you, it’s got about 18 million cracks in it, and the light is shining through like never before, filling us all with the hope and the sure knowledge that the path will be a little easier next time.”

It's hard to imagine that on that day Clinton thought she would be the one treading the path the “next time.” After all, she was 60 years old and had watched her front-running campaign collapse when faced with the natural political talent of Barack Obama. But six years later, as Obama's term entered its final turn and Democrats began seriously thinking about the 2016 election, there was Clinton. Again.

At the time, Clinton's status as the lone serious Democratic candidate in the 2016 field was touted as a virtue by party insiders. No primary! And she's by far our best candidate anyway, they argued.

The truth — as exposed by Clinton's stunning loss to Donald Trump on Tuesday night — was that the Democratic bench was (and is) remarkably thin, a sign of both the relative ill health of the party downballot and the isolated appeal of Obama.

Think about it: Why was Clinton essentially handed the nomination in early 2015? After all, she had failed once already as a front-runner in 2008. And, she represented a political theory — Clintonism — that was clearly running out of gas in an increasingly tribal and polarized political world. Not to mention that she would be 68 on Election Day 2016, not exactly the next generation of leadership for the party.

The reason for the “Clinton or bust” strategy was simple: There simply wasn't anyone else. Vice President Biden was a possibility, but the death of his oldest son, Beau, in May 2015 effectively sidelined him. (And at 73, Biden isn't exactly a spring chicken.) Beyond Biden and Clinton, name someone else who looked ready to make a serious run at a national nomination. There isn't anyone. (Trust me, I have thought about virtually every possibility.)

Contrast that to what the Republican field looked like as the 2016 election shaped up: A dozen and a half candidates including a handful of 40-something rising stars (Scott Walker, Marco Rubio, Bobby Jindal, Ted Cruz) as well as a number of other prominent voices (Jeb Bush, Chris Christie, John Kasich) within the national party who had deep and impressive résumés. And a true outsider who was making his first run for president.

That Donald Trump beat all of them is the lasting takeaway for most people. But in retrospect, the size of the GOP field — for which the party was relentlessly mocked — was also a sign of the party's health up and down the ballot. Democrats heading into 2016 simply didn't have the depth of political talent to put 10 or 12 serious candidates forward. And so they lined up behind Clinton.

Clinton's loss exposes the thinness of the Democratic bench. But it doesn't solve the problem.

Hillary Clinton spoke to supporters, Nov. 9, offering a message of thanks, apology and hope. Here are the key moments from that fervent address. (Sarah Parnass/The Washington Post)

As it became increasingly clear Clinton would lose on Tuesday night, names began to bubble up as potential 2020 Democratic candidates. Michelle Obama, who has never held or run for office, was the name I heard most. Kamala Harris, the Californian who won a Senate seat last night(!), was also mentioned. So, too, was Cory Booker, who's been in the Senate for just three years. The other names — Kirsten Gillibrand of New York, Amy Klobuchar of Minnesota — are intriguing candidates, but they almost entirely unknown nationally, even among Democrats.

One of the untold stories of the Obama presidency is how singular his victory was. Yes, Obama won more than 330 electoral votes, twice. But his success at the ballot box was never transferable. Democrats lost badly in the Senate and House in 2010 and 2014. And the damage done even further down the ballot was more grave; Democrats lost more than 900 state legislative seats in those two elections.

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The result of Obama's lonely victories — coupled with a VP pick in Biden, who was not an obvious successor given his age — was defaulting to Clinton in 2016. And in the wake of her stunning loss Tuesday night, there's a remarkable paucity of obvious 2020 candidates waiting on the Democratic bench. That's a major problem for the party, which now finds itself out of the White House for the next four years.