AP

WASHINGTON PRESIDENT Barack Obama courts voters in Florida on Thursday, opening a two-day campaign swing in a battleground state that could decide this year’s election.

If Obama can win Florida, as he did in 2008, Republican challenger Mitt Romney would have a difficult time blocking the president’s return to the White House.

The US presidential elections are not won according to the popular vote nationally but in state-by-state contests.

Obama and Romney are in one of the closest presidential contests in recent memory.

What would be a normal advantage for an incumbent president has been diminished by voter concerns over the sluggish economic recovery and 8.2 percent unemployment.

The race promises to be even closer in Florida. The state provided the deciding margin in George W Bush’s victory in 2000, and it has been closely contested ever since.

Obama aides said that since 1992, voters in the state have cast more than 32.5 million votes during the past five presidential elections, and only a total of 57,000 votes have separated the two parties in those campaigns.

“Florida’s always a close state, and we don’t expect that to change between now and November,” said Obama spokesman Ben LaBolt.

Republicans are holding their national convention in Florida in August in hopes of giving themselves an edge in the state.

Themes that have dominated the campaign should show up again during Thursday’s events.

Obama has repeatedly criticized the private equity firm Romney co-founded, Bain Capital, arguing that it promoted the outsourcing of jobs to countries like China and India.

Meanwhile, in an interview with ABC television broadcast on Thursday, Romney’s wife, Ann, said the couple would not release more tax return records.

“We’ve given all that people need to know and understand about our financial situation and about how we live our life,” she said.

Romney’s position may become increasingly untenable given that when his father made an unsuccessful run for the White House, he set a precedent of releasing tax returns covering 12 years.

He also said Obama hasn’t met with his jobs council in more than six months.

He told supporters on Wednesday that Obama’s priority “is trying to keep his own job. And that’s why he’s going to lose it.” The president was starting on Thursday with a campaign event in Jacksonville, home to a large number of veterans and military members.

Before military audiences, Obama has often talked about his efforts to bring home US combat troops from Iraq and wind down the conflict in Afghanistan.

After three days of aggressive attacks against the president, Romney moves into a relatively quiet period, with just one public event scheduled through the weekend.

Speculation about Romney’s selection of a vice-presidential candidate looms large.

Romney said on Wednesday that he has yet to make his choice, but aides say the decision could be reached as early as this week.