Bill Burton, one of the founders of Priorities USA Action, a pro-Obama super PAC, said his group had always planned to devote the fall to tying Mr. Romney to Mr. Ryan’s budget plan, but had worried that it might not stick.

“From the beginning when we polled, we found that the Ryan plan was the most toxic political document ever, but the problem was you couldn’t convince voters that any politician would actually support it,” Mr. Burton said. “Now this actually makes the job easier.”…

The Romney camp said Democrats were fooling themselves. “The race is now framed exactly as we want it,” said Kevin Madden, a senior Romney adviser. “Voters are going to judge our current struggling economy and President Obama’s lack of leadership on that issue very harshly, and then look at a Romney-Ryan ticket as an opportunity to take the country in a bold new direction towards a better future.”…

What Mr. Obama found appealing [about Ryan], the notion of a man of ideas willing to make tough choices, is what he now will need to devalue him. While Democrats openly crowed that Mr. Ryan was the choice they had hoped for because of the sharp contrast, they acknowledged he is a young, attractive, well-spoken politician who explains his plan better than his fellow Republicans do. If he makes the issue the national debt that has risen so much under Mr. Obama, rather than his solution for it, Mr. Ryan could pose a serious challenge to the president.