Mike Bloomberg knows the power that the leader of a disaster-torn city holds in American politics: Mayor Rudy Giuliani handed the mayoralty off to Bloomberg in 2001 with television ads he cut after the September 11th terror attacks.

And before he endorsed Barack Obama on Thursday, citing Obama's belief in the importance of cutting carbon emissions and the reality of rising oceans brought hom by Hurricane Sandy, Bloomberg had been practicing, in his own way, for a while. Bloomberg has ignored the new political rule that to take political stands on a human tragedy is to "politicize" it, and has repeatedly come out in the wake of mass shootings to demand stiffer gun laws.

Bloomberg endorsed Obama under the headline, "A Vote for a President to Lead on Climate Change." His 17-paragraph op-ed, published by the eponymous news service he owns and the New York Times, does not disguise his generalized disgust for both men and his lack of respect for Obama's leadership skills. Romney, he writes, "would bring valuable business experience to the Oval Office," and he attacks Obama for embracing "a divisive populist agenda focused more on redistributing income than creating it."

But Bloomberg writes that Hurricane Sandy "brought the stakes of Tuesday’s presidential election into sharp relief. He blasts Romney's reversals on the subject and concludes: "One [candidate] sees climate change as an urgent problem that threatens our planet; one does not. I want our president to place scientific evidence and risk management above electoral politics."

The endorsement may not directly move voters — Bloomberg has always been a figure primarily of the Acela Corridor — but it will dominate what remains of the political conversation around the election, and it offers validation from the same sort of moderate technocratic businessman that Romney is now presenting himself as. Obama certainly worked hard for it: The executive director of the Democratic National Committee, Patrick Gaspard, was in "constant contact" with City Hall, a Democrat told BuzzFeed.

It also turns the New York mayor, who had been searching for a next act, on the leading edge of an issue that Sandy had forced the media and political class, whose attention had wandered to the coal-heavy economies of the Midwest, to consider. Bloomberg's foundation has spent years building a climate initiative, and he has spent heavily on a push to shut down coal-fired plants. If Obama wins, the cause will finally have what it had lacked: a victory, and a political story to tell.