Barack Obama said at the start of a 48-hour campaign trip that "trust matters" in a presidential campaign and he has kept the same values throughout his political career.
The president is seeking to contrast himself with what he considers Republican Mitt Romney's shifting views.
President Obama told voters in Iowa's Quad Cities that they can take videotape of things he said 10 years ago or 12 years ago and say, quote, "man, this is the same guy".
Mr Obama says he has not finished all the work he and his supporters set out to do in 2008, but says he has fought for people every day.
Iowa is the first stop on a 48-hour trip to key states. The president said: "We're going to pull an all-nighter. No sleep."