Obama will be the featured speaker at Iowa Sen. Tom Harkin's annual steak fry in September, an event which annually draws thousands of activists.
"I think his standing has risen rapidly," Harkin said Thursday in an interview with The Associated Press.
The Illinois senator dismissed suggestions that the Iowa speech was tied to presidential ambitions.
"This is simply me accepting an invitation from Sen. Harkin, and hopefully an opportunity to assist other congressional candidates," Obama told reporters.
Obama said Harkin had been very persuasive and added, "basically my rule has been if I can help in the '06 cycle, then I'm going to do it. And the only reason not to do it has been sort of the symbolism of Iowa, which probably was not a good reason for us not to help out."