It is said that every senator looks in the mirror and sees a future president, and now Michael Bloomberg is having a similar moment of self-infatuation. Yet far more important than his idealized view of himself is what he sees in the 2020 field of Democrats.

Insiders from his camp say the former New York mayor doesn’t think any of the three leading candidates, Joe Biden, Elizabeth Warren and Bernie Sanders, can defeat President Trump.

Welcome to the club. Bloomberg’s conclusion, although self-serving, reflects a general unease among many Democrats. Mere months ago, the party was celebrating a field of 25 candidates who comprised a Noah’s Ark of group identities, but the mood has changed dramatically.

After panderfest forums, boring speeches and inconclusive debates, many Dems now sound like Peggy Lee as they ask, “Is that all there is?”

While most remain wildly enthusiastic about defeating Trump, they are far from ready to unite behind a single candidate. Even worse, the ideological split in the party is so serious that it might not be healed before Election Day.

Polls capture the problem. Biden, a relative moderate, still leads the pack nationally, but he has slipped to fourth in Iowa and is barely hanging on to second in New Hampshire. Sens. Elizabeth Warren and Bernie Sanders are second and third in most national surveys, meaning their socialist-leaning policies are popular, but neither candidate is strong enough to force the other out of the race and consolidate the far, far-left flank.

I cited that mess last month when I urged Bloomberg to get in the ring. Noting that he had flirted with running before only to pull back, I wrote that “he’s 77 years old and, his megabillions notwithstanding, he’s not getting any younger. If not now, when?”

He was hesitant because he knew he could not defeat Biden for the moderate lane, and his candidacy might end up helping Warren or Sanders. As a result, Bloomy was holding back until Biden either ­cratered or quit.

So what changed? My guess is that Bloomberg finally realized that Biden can’t go the distance. The former veep is lackluster on his best days, and his money woes are a tell that he has peaked.

Bloomy also has to know that fellow New Yorker Trump is not going to let the public forget that Hunter Biden got rich when his father was vice president. Indeed, House Dems’ bid to impeach Trump over Ukraine, Ukraine, Ukraine could well finish off their own presidential front-runner because GOP members will repeatedly shift the ­focus to the Biden family’s suspect roles there.

Still, even with all that baggage, Joe Biden might survive until it would be too late for newcomers to get into the presidential race.

Indeed, the filing deadline for the Alabama primary was Friday, and it’s this week for New Hampshire and Arkansas. Facing a yes-or-no decision, Bloomberg let it be known he intends to run.

Count me as delighted. While there’s a big mountain to climb for him to win the nomination, it is actually easy to see how he could help save the party from following Sanders or Warren into the political wilderness. That alone would be a major achievement and a service to the nation.

America succeeds when the two parties must compete for centrist voters, a fact that tends to moderate radical impulses on both sides. Trouble is, the nation is polarized, and Dems are in the process of banishing moderates, with Warren especially vicious in demonizing those who don’t agree with her pitch to break the bank on Medicare for All and other harebrained schemes.

Like an Occupy Wall Street brat, she welcomed Bloomberg into the race by ridiculing his wealth and calling him greedy. “Bloomberg has chosen to protect his wealth over everyone else — and that’s why he’d rather spend enormous amounts of money on a presidential run than pay taxes,” she wrote in a fundraising pitch.

That’s the kind of militant class warfare that turns off many in her party. One prominent New York Dem who is supporting ­Biden said while there were major ­unknowns about how Bloomberg would perform in retail politicking and debates, the former mayor would be his choice if ­Biden collapses.

“Mike’s not warm and cuddly, but I won’t support any of the others,” he said.

Another Dem veteran who worked for Bloomberg said it was important to remember that the voters the party needs to win over are in the swing states, not on the coasts. “There are large numbers of middle-class voters in the Midwest who are looking for somebody who can beat Trump and speak to the issues they care about,” he said.

As examples, he cited Bloomberg’s record of raising student test scores, creating jobs and cutting crime as issues being ignored by the other candidates. At the same time, Bloomberg is left-wing orthodox on abortion, climate change and gun control.

The easy response to the optimism is to note that there is little outward evidence that Bloomberg will be well-received on the trail. Jewish, divorced and living with a woman not his wife, a Democrat turned Republican turned independent turned Democrat again, he got just 6% support among Dems in a recent poll, with 32% saying they would never support him. Hardly an auspicious start.

But start is the key word. His willingness to open his mammoth vault gives him the ability to compete in multiple states continually and potentially tap into that yearning for someone new and closer to the center. A no-nonsense mayor, executive and philanthropist, he could honestly describe himself as a liberal with sanity.

Which is exactly what Democrats need.

The infinite stupidity of ‘racist’ math

Reader Chi Mo says Seattle has outdone New York in the loony department, writing: “Their educators want to declare math racist. This is truly sad as math is the universal language and we should be bolstering basic math education, not denigrating it. As scientists acknowledge, if there are intelligent life forms elsewhere in the universe, they may not understand any earth language, but will probably understand the math.”

Same old ‘Bull’ from anti-biz Blas

Say this for Mayor Bill de Blasio: When he gets a dumb idea in his head, it stays there. And stays there and stays there.

As The Post reports, de Blasio is again trying to move the “Charging Bull” sculpture from Bowling Green Park, citing unspecified security concerns. Last year, City Hall claimed crowd-control issues in a failed bid to move the popular bronze bull, which has been at the same spot since 1989.

Face it, de Blasio hates the bull because he hates capitalism. Maybe he’d be happier in Cuba. Or better yet, Venezuela. Go, Mayor, go!