The state shows a candidate's ability to win support in the heartland. It could help Romney in his effort to peel back states Obama won in 2008, or help Obama put Romney away.
Obama has already spent more than $2.6 million on advertising, a pace as aggressive as in any other battleground state. He's been a regular visitor, and was making his second trip in a month.
Yet the president's approval rating here has been stuck below 50 percent for over two years, softened in part by criticism from Republicans campaigning for Iowa's leadoff caucuses.
Republican Terry Branstad took back the governorship easily from Democrat Chet Culver in 2010, as the GOP won back the state House and came close in the Senate.
Polls show Iowans also have become increasingly bothered by federal spending, an issue Romney stoked in Des Moines last week in a visit where he promised to shrink the deficit.
Iowans, many of whom met Obama in the 2008 campaign, also are disappointed by what they hoped would be a transcendent presidency, said J. Ann Selzer, the longtime director of The Des Moines Register's Iowa Poll.
"You hear disaffection. You hear them say, 'This isn't what I paid for,'" Selzer said. "The guy they sent there to recast things wasn't able to do it."
Obama made his latest trip to a swing state while his campaign manager, in Washington, privately updated Senate Democrats on the state of the race. Officials said Jim Messina told lawmakers the president has several possible paths to collecting the 270 electoral votes he needs for victory in November.
But Messina also noted that Romney, the Republican Party and allied super PACs are likely to have a great deal of money to spend. Obama vastly outspent Republican John McCain in winning the White House four years ago, an advantage that Democrats appear unlikely to command in 2012.
Romney senses the opening.
He, too, has cultivated an Iowa network. Indeed, he campaigned aggressively for the 2008 caucuses during his narrowly losing bid for the state's delegates. And his campaign has begun running television ads in Iowa.
Romney and the Republican National Committee have hired state directors and are hiring staff to run a dozen or more offices planned for Iowa.
While Obama campaigned here, Romney spent Thursday visiting an inner city charter school in west Philadelphia. Romney was to spend the weekend in La Jolla, Calif., with his family.
AP Special Correspondent David Espo in Washington contributed to this story.
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