WASHINGTON, May 23: White House hopeful Mitt Romney has carved out a four-point lead on President Barack Obama in the swing state of Florida, a new poll showed on Wednesday, but the incumbent enjoys a slim nationwide lead.

With Romney cementing his grip on the Republican nomination in recent weeks and turning his full attention to a head-to-head match-up with Obama in the November election, his poll numbers have steadily improved.

He has surged ahead of Obama in the southern battleground of Florida, holding a 47-41 per cent lead, according to Quinnipiac University Polling Institute.

“The overall picture in Florida is positive for Romney, who is ahead 50-37 per cent among men, while women are divided 44-45 per cent,” the institute's assistant director Peter Brown said in a statement.

Experts and political observers are focusing on about a dozen swing states, including Colorado, Florida, New Hampshire, North Carolina and Ohio, which they predict will decide the outcome of the 2012 race.

A broader snapshot by NBC News and The Wall Street Journal, conducted after the anniversary of Osama bin Laden's death and the weak April jobs report, shows Obama clinging to a slim lead nationwide, 47-43 per cent.

But with respondents showing little confidence in the Democratic president's handling of the economy — by far the most important factor in the election — Romney remains well within striking distance.

“Obama's chances for re-election... are no better than 50-50,” said Democratic pollster Peter Hart, who along with Republican Bill McInturff conducted the survey which was released late Tuesday.

“So much has happened, and so little has changed,” Hart added. “And it tells you this is a dead-even race.”

Obama's lead in the poll stood at 49-43 one month earlier.

An ABC News/Washington Post poll released Tuesday showed the two rivals locked in a 47-47 tie on the question of who could best fix the economy, with Obama edging Romney 49-46 per cent if the election were held now.

The NBC/Journal results show respondents pessimistic about the economy, with only one in three saying they believe it will get better in the next year — down five points from April and seven points from March.

And support for Obama's handling of the economy stands at 43 per cent, down from 45 per cent last month.—AFP