Elizabeth Warren

In this June 9, 2016, file photo, Sen. Elizabeth Warren, D-Mass., speaks in Washington. (AP Photo/Nick Wass)

"It appears we're going to have an old folks' home."

That's the ever-outspoken Harry Reid, Nevada's retiring senior senator, talking about Elizabeth Warren, Joe Biden and Bernie Sanders being the unofficial early front-runners for the 2020 Democratic presidential nomination.

Warren, at 67, is the youngest of the Big Three, and she's the only one who excites both establishment Democrats and progressive activists.

But is the senior senator from Massachusetts game for a presidential run? Some pundits believe she's already positioning herself for it.

Warren, the former guiding light of the Consumer Financial Protection Bureau, recently announced she's joining the Senate's Armed Services Committee. "As a member of the committee, I will focus on making sure Congress provides effective support and oversight of the Armed Forces, monitors threats to national security, and ensures the responsible use of military force around the globe," she said in a statement.

MSNBC commentator Lawrence O'Donnell, a former legislative aide to the late Democratic Sen. Daniel Patrick Moynihan, noted that the Armed Services Committee will nicely fill out Warren's C.V. with needed foreign-policy experience and insisted the move "could be a first step in a presidential campaign."

But 2020 might be too late for Warren. History shows that politicians typically only get one really good shot at the presidency, one moment when ambition lines up with the mood of the country. Ask John McCain (2000) -- and Hillary Clinton (2008). Warren very well might have already missed her shot.

The conventional view of the race for the 2016 Democratic nomination is that Sanders' success was a shock, that no one realized his anti-Wall Street, "We're the 99%" message would have such resonance among voters. But while the former is indeed true, the same can't legitimately be said of the latter.

Here was the Wall Street Journal's John Feehery way back in July 2014: "If Democratic primaries were held only on Wall Street and in Washington, former secretary Clinton would trounce Sen. Warren. But in the rest of the country, it would be a different story."

In 2014 and early 2015, it was Warren, not Sanders, who thrilled progressives. A well-funded, grass-roots draft-Warren effort was launched, rolling out an online petition and inundating her with pleas from Democrats across the country. The group even staged a "fun run" past her Senate office, with supporters blowing horns while decked out in "Warren for President" and "Run, Elizabeth, Run!" gear.

Washington Post columnist Dana Milbank wrote that the effort was "eerily similar to the movement that propelled Barack Obama to challenge Clinton eight years ago."

Milbank, like Feehery, recognized there was an opening for her -- "a feisty populist at a time of inequality and resentment." But he also wondered if she was up for it, noting that her in-the-weeds approach to her Senate work "suggest she has neither interest in nor aptitude for a presidential candidacy."

It turned out he was right. Warren saw that Clinton was calling in her chits among party leaders and so decided to take a pass on a presidential run, leaving it to Sanders -- a grouchy, far-left independent who had never been a member of the Democratic Party -- to challenge the tottering, centrist Clinton empire.

Some progressives haven't gotten over it. They say Warren's refusal to take on Clinton is the reason Republican Donald Trump is now the president-elect, that Warren surely would have won the nomination and the White House. And they doubt she'll step up four years from now. If she didn't have the courage or the fire in her belly for an intraparty fight against Clinton, they point out, why would she take on a sitting president -- surely an even bigger and more difficult battle?

This much is certain: time moves on quickly for politicians with national aspirations. Warren will be 71 in 2020, and, as Reid suggested, Democrats are starting to think about how they need new, younger leaders. New Jersey Sen. Cory Booker is often mentioned as a possible party standard-bearer, as is New York Sen. Kirsten Gillibrand. Increasingly, Democrats are holding out hope that someone not yet on the national radar will, like Barack Obama in 2004, suddenly leap to the fore.

Of course, Warren might run in 2020 anyway. If so, she very well could be the galvanizing candidate progressives believe she would have been in 2016. Or, like McCain eight years ago and Clinton this year, she could fail to muster the enthusiasm she had generated at an earlier time, in a very different political world.

-- Douglas Perry