What is most striking about Michael Bloomberg’s endorsement of Barack Obama—announced, unexpectedly, on Thursday afternoon—is that it could not be ascribed to a single aspect of the Mayor’s persona or philosophy. This was not an act of political obligation, or some poignant, Chris Christie-like expression of gratitude for Obama’s help in handling Hurricane Sandy, even though Sandy is what decided Bloomberg—what, as he writes, “brought the stakes of Tuesday’s presidential election into sharp relief.” Until now, Bloomberg had maintained the stubborn view that he didn’t have to take sides or tell anyone what he thought—he was the last undecided voter, his own private Ohio. Bloomberg is a billionaire who ran as a Republican but now calls himself an independent. “Like so many other independents, I have found the past four years to be, in a word, disappointing,” he wrote in his endorsement, adding that Obama had “embraced a divisive populist agenda focused more on redistributing income than creating it.” This is not about the forty-seven per cent, or payback for FEMA money coming into Manhattan. The Mayor has not become a different person. But while looking at the storm and what it did to our city, his eyes were watching something else:

Our climate is changing. And while the increase in extreme weather we have experienced in New York City and around the world may or may not be the result of it, the risk that it might be—given this week’s devastation—should compel all elected leaders to take immediate action.

That was the tiebreaker; this is what matters. Bloomberg has some memories of a Mitt Romney who once embraced carbon taxes; he, and the rest of us, now have a clearer memory of a Romney who mocked the very idea of doing something to “slow the rise of the oceans.” We do have to slow them, or fundamentally change many of the structures we rely on, and Bloomberg, with the confidence of a man who made a few billion dollars, seems to believe that he can. Obama may not have succeeded yet, but Bloomberg wants someone who wants to try. One candidate, he says, “sees climate change as an urgent problem that threatens our planet; one does not.”

Bloomberg’s endorsement will be taken more seriously precisely because it is against character. The Mayor’s caveats in public today do not even begin to reflect his ambivalence about President Obama. Sources say that in private he can be scathing about Obama, though it is never clear whether the Mayor is most offended because of the President’s ideology or because, well, the President is the President and the Mayor is not and probably never will be. Ego aside, in social settings Bloomberg is blistering on the subject of Obama’s economic policies and political skills. Bloomberg, a creature of Wall Street, sees the President as unnecessarily hostile to bankers and maddeningly unable to reach the sort of “grand bargain” needed to stabilize the American economy and its ledgers. Bloomberg’s idea of the ideal politician is Bloomberg, and he faults Obama as diffident and, at times, in over his head. But Bloomberg has even greater contempt for Romney’s vacillations, and for his willingness to turn away from a Bloombergian pragmatic centrism to an ever-shifting Republicanism that never risks losing the support of the far-right. Obama, Bloomberg concluded in his endorsement, can “lead our country toward a better future for my children and yours. And that’s why I will be voting for him.”

When I step into the voting booth, I think about the world I want to leave my two daughters, and the values that are required to guide us there. The two parties’ nominees for president offer different visions of where they want to lead America.

The same balancing game can be seen in the other two factors Bloomberg singles out as decisive: “One believes a woman’s right to choose should be protected for future generations; one does not. That difference, given the likelihood of Supreme Court vacancies, weighs heavily on my decision.” And “one recognizes marriage equality as consistent with America’s march of freedom; one does not. I want our president to be on the right side of history.”

So how historic is Bloomberg’s announcement—how much does it matter? It is a genuine surprise, and that will give it more weight. Independents should notice. And this race is so tight. Also, again, Bloomberg is a billionaire. If an endorsement means that he will spend money, he is not only a voice but a force. (It was endorsement ads by Rudy Giuliani, in the wake of another disaster—9/11—that helped seal Bloomberg’s first mayoral victory.) There are five days until the election, and this is a top story on one of them.

But Bloomberg’s endorsement may matter for more than Obama or this election. It also says something powerful about the three issues Bloomberg singled out as mattering for his daughters’ future. The Supreme Court and a woman’s right to choose have long been central to one’s thinking in the voting booth, but Bloomberg has provided more confirmation that gay marriage is becoming a centrist position. And the biggest winner here may be for the fight to make climate change something other than what Elizabeth Kolbert called the great unmentionable. Many more in New York and New Jersey have begun listening, and speaking out, this week—by making it a matter of the national race, maybe Bloomberg will help get the rest of the country to pay attention, too. Maybe candidates can throw off their agnosticism and know that they will have the support to win; maybe we can stop pretending that a march of disasters is a coincidence. Whether Obama wins or loses, did the fight to keep the world above the water just move a step forward?

See our full coverage of the campaign season at The Political Scene.

Photograph by Photograph by Seth Wenig/AP.