The president's hopes of a second term in office received an immediate boost from New York's Mayor Michael Bloomberg, who has previously sat on the fence over who to support in Tuesday's tight poll.
Mr Bloomberg, who at different times has been both a Democrat and a Republican but is now independent, said the devastation of the storm "brought the stakes of Tuesday's presidential election into sharp relief".
He said Mr Obama was the best candidate to lead the fight against climate change and that Republican candidate Mitt Romney had "reversed course" on previous environmental stances.
The billionaire also backed Mr Obama's stance on gay marriage and abortion.
"If he listens to people on both sides, and builds the trust of moderates, he can fulfil the hope he inspired four years ago and lead our country toward a better future for my children and yours," Mr Bloomberg said.
The endorsement will provide welcome relief for the President in the tight race.