With Republican voters just beginning to narrow down their field of candidates, Obama said there were reasons to look forward to the rest of the campaign that will culminate in the Nov. 6 general election, and beyond.
When Roseann Cook of Coralville, Iowa, asked him if he still believes in "hope and change in America," the Democratic president replied: "In some ways, I'm actually more optimistic now than when I first ran. We've already seen change take place. 2012 is about reminding the American people how far we've traveled."
Obama, who received cheers from the Iowa crowd, mentioned his administration's record of ending the war in Iraq, getting healthcare reform through Congress and easing the financial burden of college students.
He criticized Republicans for supporting "tax cuts for the wealthiest among us" and said "it's going to be a big battle" fending GOP efforts to help the wealthy and "roll back regulations on clean air and Wall Street reform."
When Carol White of Cedar Rapids asked him how he responds to people who say he hasn't done enough, Obama said: "We've done a lot and we have a lot more to do. That's why we need four more years."
White House spokesman Jay Carney told reporters earlier Tuesday he expected the president would keep abreast of the GOP results in Iowa.
"Like many of us he will, I'm sure, be interested to see what the results are in the other party's caucuses," Carney said. "I'm sure he is ... no more or less interested than the rest of us."