Democrats debate: Revolution or restoration.

The Democratic presidential race is ultimately a debate about whether to promise America a revolution or a restoration.

For much of 2019, revolution seemed to be winning. But then, in late November, a Quinnipiac University poll showed Elizabeth Warren losing half her support in just one month and Joe Biden retaking the lead.

Restoration now seems ascendant.

In October, Quinnipiac’s nationwide poll showed Warren leading with 28 percent, Biden at 21, Bernie Sanders 15 and Pete Buttigieg 10. In the November poll, Warren dropped 14 points. It was Biden 24, Buttigieg 16, Warren 14 and Sanders 13.

Warren’s drop was attributed to questions about and criticism of her Medicare For All plan, including how to pay for it and how people would react to losing their current insurance.

But there may be more to it.

Warren got the tough scrutiny at precisely the same time Democrats were watching the Trump impeachment hearings. The hearings reinforced their fear and loathing of Trump. They were reminded that, above all, they don’t want him reelected.

They might then have said: “Do we risk Trump winning if we nominate somebody who’s proposing big government programs?”

They might also have said: “Since Trump wanted Ukraine to investigate Biden, maybe he’s scared of Biden and Biden is our best bet to win.”

Look at the poll another way. Combine the numbers for the two “revolution” candidates: Warren, whose slogan is “Dream Big. Fight Hard,” and Sanders, who calls for a “Political Revolution.” Then combine the numbers for the two “restoration” candidates: Biden and Buttigieg, who propose more incremental change and promise a return to civility, normalcy and even bipartisanship.

In October, “revolution” led 43-31. In November, “restoration” led 40-27. That’s a 25-point swing.

The November poll showed how much electability matters: 35 percent of voters said it’s their top consideration. Tied for second, with 19 percent each, were “honesty” and “cares about people like you.”

Almost half the voters, 46 percent, said Biden is the candidate “who has the best chance of winning against Donald Trump in the 2020 presidential election.” Ten percent each said Warren and Sanders, and six percent said Buttigieg.

Still, even Biden’s supporters feel shaky about his sometimes-shaky performances in debates and campaign events.

If Biden falters, does Buttigieg inherit the Restoration mantle? Or is there an opening for, say, Amy Klobuchar, Cory Booker or Michael Bloomberg?

Bloomberg’s $30 million-a-week TV blitz aims right at Medicare For All. He says he’d see that “everyone without health insurance can get it, and everyone who likes theirs can keep it.”

The Revolution/Restoration debate is fueled by ideological and generational tensions among Democrats. Liberals like big promises: Medicare For All, a wealth tax, free college tuition and Green New Deal. Moderates don’t argue with big goals but are more cautious about how to reach them.

Millennials and Generation Z voters are more willing than Baby Boomers and Silent Generation voters to embrace big changes. Younger voters are more economically stressed and more concerned about the coming climate catastrophe.

The Democrats’ debate over “Dream Big” or “Just Win” is far from resolved. But, for now, Just Win is winning.