Obama -- at the start of a 48-hour, cross-country marathon that took him to six swing states, as well as Los Angeles and Chicago -- spoke to 3,500 supporters at the Mississippi Valley Fairgrounds in Davenport, Iowa, about his rival's "Romnesia," the inability to remember past policy positions.
"So two weeks from the election -- because he knows that if he actually told everybody what he wants to do he probably wouldn't get any votes, so he's doing everything he can to make sure that you don't notice what he's been saying," Obama said to laughter.
"We're gonna pull an all-nighter!" Obama said. "No Sleep! We're starting in Iowa, then we're gonna go to Colorado, then Nevada, California, then we're gonna go to Florida, then Virginia, Ohio, and then we're going to Illinois to vote."
Romney held a rally in Reno, Nev., and then went to Cedar Rapids, Iowa, before heading for Ohio.
Obama's cross-country marathon followed appearances Tuesday in Florida and Ohio.
"We are doing this now because we see this as a pivotal time in the election," campaign spokeswoman Jen Psaki told reporters aboard Air Force One.
Republican vice presidential nominee Paul Ryan, campaigning at Cleveland State University, said too many barriers still confront minority children, especially when it comes to access to quality education.
"That's unacceptable," Ryan said. "We owe every child a chance to succeed."
Campaigning Marion Harding High School in Marion, Ohio, Vice President Joe Biden's remarks were interrupted by a baby.
"I don't blame that baby for crying," Biden quipped. "You know what, she just realized what it means if Romney gets elected."
In an announcement on Twitter, Mega-millionaire real estate developer Donald Trump says he'll give $5 million to charity if President Obama releases his college and passport records.