Republican challenger Mitt Romney is swinging back to familiar issues, including the struggling US economy and his looming choice of a vice-presidential running mate, after a gaffe-prone overseas trip.
Three months remain before the November election, and the political parties' nominating conventions are drawing near. President Barack Obama was making his ninth trip to the all-important battleground state of Ohio on Wednesday.
A new poll of voters there and in two other key states, Florida and Pennsylvania, showed Obama with a clear advantage going into the national conventions.
The Quinnipiac University/New York Times/CBS News polls found Obama with a six-percentage-point lead over Romney in Florida and Ohio. The president was up by 11 percentage points in Pennsylvania.
Obama has returned to hammering Romney over tax policy after largely standing aside during a week in which Romney repeatedly engaged in diplomatic stumbles during his journey to Britain, Israel and Poland.
US foreign policy had a brief interlude as a campaign issue during Romney's trip abroad, but both candidates again are focusing on the economy, the top concern of voters in what is forecast to be one of the closest US presidential elections in recent history.
Polls show Romney with a sizable advantage over Obama as the best candidate to revive the wobbly economy, and the president is countering by urging the Republican-controlled House of Representatives to extend Bush-era tax cuts for all but the highest-earning Americans. Romney has proposed cutting taxes for everyone, including the wealthy, and making the Bush tax cuts permanent for all income levels.
The issue of taxes, however, cuts both ways. Democrats and some leading Republicans are calling on Romney to release more of his income tax returns. Romney, who would be among the nation's wealthiest presidents if elected, has released just one year of personal income tax returns and promised to release a second, but no more.
By travelling to Ohio yet again, Obama was acknowledging the critical nature of that state for his chances of winning a second term.
The US president is not chosen by popular vote but in a series of state-by-state contests. With the race near deadlock for months, both candidates are aggressively courting a relative sliver of undecided voters who live in eight or so states that are neither reliably Republican nor Democratic.
Obama believes he can carry Ohio again this year, banking on voters' receptiveness to his record on taxes and manufacturing, particularly his decision to rescue General Motors and Chrysler in 2009. Ohio's economy is heavily dependent on the auto industry.
Obama's campaign released a new ad Tuesday saying Romney's approach on tax cuts, coupled with increased military spending, would add "trillions to the deficit." The spot was airing in Colorado, Iowa, New Hampshire, Nevada, Ohio and Florida, battleground states where polls show the candidates separated by only a few percentage points.
Romney was spending Wednesday in private meetings at his campaign's Boston headquarters as speculation swirled about the selection of his vice-presidential candidate. The campaign was preparing to ramp up his public schedule in the weeks leading up to the Republican National Convention at the end of August.
Romney also was running a new television commercial that suggested another immediate priority was to close a likability gap in the polls. While the voting public generally believes Romney has better economic policies than Obama, it views the president in more favourable terms personally.