New York Mayor Michael Bloomberg has backed President Barack Obama over Republican Mitt Romney, saying the incumbent Democrat will bring critically needed leadership to fight climate change after the devastation wrought by Superstorm Sandy.
The endorsement on Thursday from the politically independent mayor of the biggest US city was a major boost for Obama, who is spending the campaign's final days trying to win over independent voters whose voices will be critical in determining the winner of Tuesday's election.
Both candidates had eagerly sought the nod from Bloomberg, who did not endorse a presidential candidate in 2008 and has publicly grumbled about both Obama and Romney. But Bloomberg said the possibility that Sandy resulted from climate change had made the stakes of the election that much clearer.
"We need leadership from the White House, and over the past four years, President Barack Obama has taken major steps to reduce our carbon consumption,'' Bloomberg wrote in an online opinion piece for Bloomberg View.
Obama was back on the the campaign trail on Thursday, after a three-day pause to manage the federal response to the deadly storm that battered the East Coast.
His first stop was Wisconsin, where he was making up for an event that was cancelled earlier in the week because of the storm. He had rallies planned later in Las Vegas, Nevada, as well as Boulder, Colorado, a heavily Democratic area of the swing state.
| Patty Culhane reports on Obama in Las Vegas, Nevada
Polling shows the presidential race essentially tied nationally ahead of Tuesday's vote. The incumbent was backed by 47 per cent of probable voters and Republican challenger Romney supported by 46 per cent in a Reuters/Ipsos poll presented on Thursday.
Romney aimed at patriotism and the heartland as he was campaigning in Virginia on Thursday, mentioning Boy Scouts, football, "America the Beautiful" and the flag.
He also criticised Obama's comment in an interview aired by MSNBC on Monday that he would like to consolidate government agencies that deal with business issues in a new department under a secretary of business.
"I don't think adding a new chair to his cabinet will help add millions of jobs on Main Street," Romney said.
The last of the closely watched monthly unemployment reports comes out on Friday. Last month's report said unemployment had dipped below eight per cent for the first time since the month Obama took office.
In Wisconsin, Obama returned to the aftermath of the storm, saying he saw yet again "that there are no Democrats or Republicans in a storm. There are just Americans".
Obama has been given high marks, even from some of his harshest Republican critics, for his handling of this week's storm crisis and the dispatch of massive federal aid to victims.
Romney has been forced to answer questions about his earlier campaign statements that the key federal emergency relief organisation, the Federal Emergency Management Agency, should turn its role over to the states.
Live Box 20121816112138306
Obama also resurrected his 2008 "change" slogan and said he was the only candidate who had actually fought for it.
"You may be frustrated at the pace of change, but you know what I believe, you know where I stand," Obama told a crowd on an airport tarmac. "I know what change looks like because I've fought for it."
Both candidates will spend the final days in eight swing states that will decide who wins the electoral votes needed to capture the White House.
Obama holds slim leads in a majority of the so-called battleground states. Those states are neither reliably Republican nor Democratic, giving them outsized importance in the US system for choosing the president.
The winner is not the candidate with the most popular votes nationwide but the one who manages to accumulate at least 270 electoral votes in state-by-state contests. Those votes are determined by a state's representation in Congress.
Despite a Romney surge nationwide after the three presidential debates, polling shows Obama holding on to leads in enough of the all-important swing states - most notably Ohio - to win at least the necessary 270 electoral votes. No Republican candidate for the White House so far has won the election without capturing Ohio.
More than 19 million people have already voted, either by mail or in person.