VIRGINIA BEACH, Virginia (AFP) — US President Barack Obama and his Republican opponent Mitt Romney engaged in a long-distance joust in swing states yesterday, each seeking an edge in the post-convention race for approval.

With the Democratic and Republican national conventions a fading memory, and little sign of a discernible bounce for either candidate, the pair will grind it out over the next two months in a neck-and-neck race to November 6.

While Obama courted voters in the biggest US battleground state, Florida, Romney was in hotly contested Virginia, seeking to build momentum one day after a weak US jobs report gave him an opening to lure undecided voters.

The mission is to "persuade a lot of these voters who have yet to be persuaded", is how Romney adviser Kevin Madden described the task to reporters before the candidate arrived in Virginia Beach for a rally.

"That'll be what these next 60 days is about, is talking directly to the issue that they care about most, which is the economy and making the case that the governor can get the country going in the right direction."

Obama, Madden argued, has had four years to be judged, "and they've judged him pretty harshly. That's the reason why they're undecided, is because they haven't been persuaded that the president is doing a good job."

Romney appeared to have cornered the thrill market for yesterday, heading to a NASCAR race, the Federated Auto Parts 400 under the lights at Richmond International Raceway, after a rally in Virginia Beach.

It will be his second NASCAR race of the season, and Romney is hoping for a smoother outcome this time around.

At the Daytona 500, the multimillionaire former private equity boss infamously said that while he does not follow races as closely as ardent fans, he considers several NASCAR team owners to be friends -- a comment that helped solidify his image as a man out of touch.

Obama, meanwhile, set off on a two-day tour of Florida in his sleek, black armoured vehicle, trundling along the most keenly contested area of the state -- highway I-4, which is seen as the dividing line between the more conservative north and more Democratic south.

And in his first rally of the day, in front of a solid crowd of 11,000, the president was introduced by Charlie Crist, Florida's former Republican governor who later quit the party and became an independent and who now backs Obama.

"We have a leader with a cool head, his name is President Barack Obama," Crist said in St Petersburg, close to the Tampa site of the Republican convention two weeks ago.

"He is working hard for the middle class, he is working hard for Florida," added Crist, who was defeated in a Senate primary campaign in 2010 by Marco Rubio, a rising star Republican who was backed by the Tea Party movement.

Obama was due to motor coast-to-coast across to Orlando, and end the Florida trip in West Palm Beach today.

"If President Obama carries Florida, with its 29 electoral votes, that is the election," said Florida Senator Bill Nelson, a Democrat. "Where is the swing part of the state of Florida? It is right here in the I-4 corridor."

Several tracking polls signal a slight post-convention boost for Obama, with his Gallup approval ratings up three points to 52 per cent, above the 50 per cent threshold considered mandatory for a president to be re-elected.

The data could indicate a warm reception for the convention speeches of First Lady Michelle Obama and former president Bill Clinton, as most of the voter interviews were conducted before Obama took the stage on Thursday night.

Despite some tepid media reviews of Obama's keynote address, the Obama campaign insists it worked.