Mitt Romney declined to say how he disagreed with his running mate on the issue of Medicare reform, despite taking three different versions of the question from reporters in a press conference Monday.

In the 72 hours since Romney tapped Paul Ryan to join him on the Republican ticket, his campaign has repeatedly insisted that he won't be adopting the Congressman's bold, and controversial, plan to turn Medicare into a voucher system, with aides saying he doesn't agree with his running mate on every issue. But asked where, exactly, he disagreed with Ryan, Romney demurred.

"The items that we agree on far outweigh the things we disagree on," he said, adding later, "I can't imagine any two people who have exactly the same positions on the same issues."