Obama said he'd kept his promises to end the war in Iraq, expand health insurance, kill Osama bin Laden and allow openly gay soldiers to serve in the military. He said Romney's presidency would return the nation to the "top-down economics that crashed our economy."
"What he's selling, we tried. It didn't work. We're not going back," he said. He told supporters to knock on doors and "turn out the vote for me" on Tuesday.
Mellencamp had warmed up the crowd, strumming an acoustic guitar and singing his hits, including "Jack and Diane" and "Small Town."
"The middle class needs to rise up and be strong. Let's let them rich pay more than 14 percent," Mellencamp said, a reference to Romney's income tax rate.
While undecided voters were the prize, mostly faithful supporters of the candidates attended the events. Obama noted that many of his supporters had already voted in Iowa thanks to early voting.
Elections officials say about 40 percent of the electorate in Democratic-leaning Dubuque County has voted early, and more cast ballots at a downtown office annex Saturday.
Some Dubuque residents went to see both candidates, saying they wanted to witness history. They included Olivia Griffin, an education major at the University of Dubuque who had already voted for Obama but waited in line to see Romney with her boyfriend's family anyway. She had a ticket for the Obama event later Saturday.
"When else are you going to get a chance to see both candidates in one town in the same day?" she said. "It's going to be fun."