The First Read gang reports that Obama will attack Mitt Romney over his support for the Paul Ryan Medicare plan when he campaigns in Florida today:

Today when Obama begins a two-day swing through the crucial state of Florida — with all of its seniors — he’ll introduce another attack: hitting Romney on Medicare and the Ryan budget. Per the campaign, the president “will discuss his commitment to strengthening Medicare, and a new report tomorrow that highlights the devastating impact Mitt Romney’s Medicare plan could have on the 3.4 million Floridians that rely on Medicare.”

Bottom line, per the campaign’s guidance: Obama will argue that Romney — through his support for the Ryan budget plan — advocates ending Medicare “as we know it.”

Ed Kilgore and Jonathan Chait note that this is the start of a new and important phase in the campaign, i.e., the battle over the Paul Ryan budget, which has become the blueprint for the GOP economic agenda and the larger set of values and priorities Republicans would bring to tax reform, entitlements, and balancing the budget.

Keep in mind: A focus group convened by the pro-Obama Priorities U.S.A. found that voters simply refused to believe that Romney or Ryan would really transform Medicare into a quasi-voucher program while also cutting taxes for the rich. This is what the assault on Romney’s Bain years is really about. It’s an effort to establish an image of Romney that will make it easier for voters to accept that this is indeed the agenda Romney has embraced and would carry out as president.

As the Obama campaign will point out, Republicans expect Romney to essentially rubber-stamp the Ryan’s agenda. ”We want the Ryan budget,” Grover Norquist recently said. “Pick a Republican with enough working digits to handle a pen to become president of the United States.”

The attacks on Romney’s business background and core rationale for running for president may enable the Obama campaign to fight Romney to a draw on the economy — by persuading swing voters who are unhappy with Obama’s performance that Romney certainly doesn’t have the answers to their economic problems, and could even make things worse. (This could become much harder if the economic news worsens, but it’s possible.)

If so, more of the campaign could end up being fought out on other territory, such as entitlements and tax fairness. Obama will perhaps be able to argue to swing voters that entitlements will simply have to be overhauled, and when it comes down to it, he’s the one that they should trust to protect their interests when crunch time hits, rather than Romney and Ryan, who are more willing to cut things they like in order to keep taxes low on the rich. Of course, Obama first has to figure out how to make enough voters believe this about them.