(VOVworld) - US incumbent president Barack Obama and Republican challenger Mitt Romney are on a final dash to win undecided votes. Recent polls show Obama with a slight edge over Romney in key states.

Barack Obama and Mitt Romney in their presidential campaign trails (Photo: AFP)

The Pew Research Center in its latest opinion poll on Monday showed Obama with a modest lead of 48%-45% over Romney. Iowa’s Des Moines Register reported that the national popular vote is Obama 47% and Romney 42%, while the figure in Ohio, as reported by the Columbus Dispatch, is Obama over Romney 50% to 48%. Romney is desperate to turn the tide in Ohio. He told Ohio voters this week: I’ve asked them to put aside all speeches, all advertisements, and all the attacks, and to look at the records. Because the talk is cheap but the record is real and it is earned with real efforts. Change is not measured in words or speeches. Change is measured in achievements

No Republican has ever been elected president without winning Ohio. Opinion polls in New Hampshire show Obama and Romney with equal support. In order to tip the equilibrium, former President Bill Clinton, who is popular with both Democrats and independents, joined Obama on the campaign trail. Clinton spoke today to some Concord, New Hampshire, residents: In the 7 years of the previous administration when they follow the same policy that Governor Romney recommended they had 2.6 million jobs. So you got 2.5 year and 5.5 million jobs. The same policy. I’m telling you to compare to what happened. Barack Obama has done a good job.

Florida’s polls show a mixed message. The NBC, Wall Street Journal, and Marist polls announced last Saturday that Obama’s support was 2% ahead of Romney’s, while the Mason Dixon poll had Romney ahead by 6 points.

Nhat Quynh, Huy Hoang, VOV correspondents in Washington