Politics, now. Two days until what could be the biggest event so far for mitt romney's campaign. As we head into the republican national convention, romney cannot seem to get out of his own way,... See More
Politics, now. Two days until what could be the biggest event so far for mitt romney's campaign. As we head into the republican national convention, romney cannot seem to get out of his own way, veering off-message for what some are calling an ill-timed joke about the birther issue. David kerley in washington and on the story. David, good morning to you. Reporter: Dan, he is calling it, mitt romney, humor. But the headlines are blaring about the latest roadblock that mitt romney has put up himself on the way to tampa. Mitt romney rolled into michigan, hoping to gain some momentum leading into the convention. He bragged about being born here. But then, dragged up the disproved birther issue, suggesting the president wasn't born in the u.S. And I was born at harper hospital. No one's ever asked to see my birth certificate. They know this was the place we were born and raised. Reporter: In an interview with cbs, romney said, that was just a little humor. Not a swipe. I said throughout the campaign and before, there's no question ion about where he was born. He was born in the u.S. Reporter: But the obama campaign pounced. Calling it a new low. But this issue has become a joke on the obama website, where for 22.50, you can buy a mug with made in the usa over the president's picture and a copy of his birth certificate on the other side. It's just the latest distraction for the romney team. We will lead. Reporter: First, it was paul ryan's medicare plan that dominated headlines for more than a week. And then, the abortion and rape discussion after the comments of a republican senate candidate. There's some people who are having trouble understanding our message. Reporter: All, as the campaign hopes to turn next week's convention into an opportunity to introduce romney and try and set a tone of optimism for the future. We're going to talk about the soul of america. What makes this nation unique and exceptional on the history of the earth. Reporter: In fact, in tampa, expect to hear a lot of republican rhetoric about the future. America will stay strong and prosperous and free. And the hope of the earth. Thank you so very much. Great to be with you. Thank you. Reporter: Meanwhile, the president is happy to talk about just about anything other than the latest jobs numbers. And this morning, he uses his weekly radio address to make his claim that he has strengthened medicare. Dan, he's putting out a new ad today in battleground states, saying that mitt romney would break the promise of medicare. David kerley, thank you. A reminder, tomorrow morning, george stephanopoulos kicking off our convention coverage on "this week," with a faceoff between the chairman of the republican platform committee and the head of the democratic national convention.
This transcript has been automatically generated and may not be 100% accurate.