Where are all the Democrats? Candidates, that is. The putative front runner, Hillary Clinton, sent out a tweet that she’s running and hasn’t been heard from since, except for being mired in the scandals of her e-mails, “non-profit” foundation and Benghazi.

All sorts of Republicans are jumping into the GOP race. Dr. Ben Carson, former Governor Huckabee and Carly Fiorina are the latest. This is in a field already crowded with such heavyweights as Senators Marco Rubio, Ted Cruz, and Rand Paul. And Governor Jeb Bush is exploring.

Yet almost no one is rising to the challenge of running for the Democratic nomination. There is an ex-mayor, Martin O’Malley, who has been making noises about running. But the city he was mayor of lies in ashes, a symbol of the failure of liberal Democratic urban politics.

Senator Bernie Sanders, a Socialist from Vermont, is the only candidate so far who has declared against Hillary Clinton. Governor Cuomo is mired in scandal himself, after closing down the Moreland Act Commission that was supposed to clean up Albany.

So what about Mike Bloomberg? Last week out of the blue, I had an e-mail from a friend who knows the ex-mayor, and he thinks this is the moment for a “Draft Mike” movement. He’s the “best person to lead the Democrats,” my friend wrote.

“Elizabeth Warren would be dramatically worse,” he added.

That got my number. Back in 2008, I wore my fingers to stubs writing New York Sun editorials encouraging Mr. Bloomberg to throw in his hat as an independent. Hizzonor rewarded me by leaking his definitive decision against doing so to . . . the New York Times.

To hell with him, I thought. I wasn’t planning to vote for him anyhow, though I did like the idea of having an outspoken New Yorker in the race. Particularly one who could carry an unbridled pro-immigration, pro-business message away from which others were shying.

Mr. Bloomberg thought it was unlikely he could win as an independent. A short, Jewish guy who’s for gay marriage and against gun rights isn’t going to make it, he told various friends around town. My own theory is that he feared tipping the race to a GOP with which he’d come to feel uncomfortable.

For Mr. Bloomberg to run as a Democrat, though — that’s a whole different story. He supposedly was a Democrat, after all, before he was a Republican and then an independent. So at least in part this would be a Bloomberg-comes-home story.

And it’s got a good plot. All of us had plenty of gripes about the way Mr. Bloomberg ran New York, but the city boomed under his leadership. Building was way up, and crime was way down, and he knew how to defend cops and back Police Commissioner Kelly.

If he’d lasted in office long enough, I believe, he’d have won the stop-question-and-frisk case in the Court of Appeals. The NYPD’s vigil against another terrorist strike set a model that other cities (and the federal government) could study as ISIS vies for an American foothold.

Mr. Bloomberg’s early endorsement of same-sex marriage, even for those of us who worry about how it will isolate religious Americans, may not be as crosswise with the voters in 2016 as he feared it was in 2008. I disagree with him on guns but admire his stubbornness.

Mayor Bloomberg understood the competitive challenges facing New York markets from overseas, and he guided the city through a historic budget crisis in the wake of 9/11. He became a champion of charter schools, the most exciting school reform of his time.

One has to figure that Mr. Bloomberg, liberal though he is, would never have gotten into the kind of fight with Prime Minister Netanyahu that President Obama and Secretary of State Hillary Clinton did. And he would be much tougher, one can guess, in negotiations with the Iranians.

The ex-mayor could also self-fund a presidential campaign, even a big one, and rich as Mr. Bloomberg is, he doesn’t seem entirely comfortable merely counting his cash. There was a story the other day that he was thinking of running for mayor of London.

Why, though, bow to Queen Elizabeth? He’d be better off if he stayed home and ran against Queen Hillary. At the rate things are going, she could yet abdicate.

This column first appeared in the New York Post.