The president also has run more than $20 million in ads, including many that characterize Romney and his positions as those of a wealthy, detached former business executive. Obama allies also have spent roughly $3 million in advertising.
Obama aides say Romney's criticism of Obama's handling of the economy has been less effective here than it has been in states such as harder-hit Florida and Nevada. In August, Iowa unemployment was 5.5 percent, up from July but far below the national average of 8.1 percent.
But Obama aides also say Romney hasn't made as much of an effort to build a personal connection with voters in a state where face-to-face campaigning is key, and they say his comment about 47 percent of Americans who don't pay federal income tax has been problematic.
"He doesn't think poor people are his problem," Oskaloosa Democrat Pam Douglas said. "They are his problem if he wants to be president."
Associated Press writer Julie Pace in Chicago contributed to this report.