The Obama campaign has released an ad attacking Mitt Romney's selection of Rep. Paul Ryan as his running mate—and links to a website with five facts about Ryan, such as, "Paul Ryan’s extreme budget would end Medicare as we know it, turning it into a voucher program which would increase seniors’ health costs by $6,350 a year. Ryan has also proposed a plan that would have privatized Social Security, subjecting seniors’ retirement security to the whims of the stock market."

Obama campaign manager Jim Messina released a statement, too:

In naming Congressman Paul Ryan, Mitt Romney has chosen a leader of the House Republicans who shares his commitment to the flawed theory that new budget-busting tax cuts for the wealthy, while placing greater burdens on the middle class and seniors, will somehow deliver a stronger economy. The architect of the radical Republican House budget, Ryan, like Romney, proposed an additional $250,000 tax cut for millionaires, and deep cuts in education from Head Start to college aid. His plan also would end Medicare as we know it by turning it into a voucher system, shifting thousands of dollars in health care costs to seniors. As a member of Congress, Ryan rubber-stamped the reckless Bush economic policies that exploded our deficit and crashed our economy. Now the Romney-Ryan ticket would take us back by repeating the same, catastrophic mistakes.

In his May profile of Ryan in New York, Jonathan Chait wrote, "Romney has shown no inclination to challenge Ryan, praising him fulsomely and even promising him, according to The Weekly Standard’s Stephen Hayes, he’d enact Ryan’s plan in the first 100 days. Republicans envision an administration in which Romney has relegated himself to a kind of head-of-state role, at least domestically, with Ryan as the actual head of government."

The Romney campaign has its talking points to rebut attacks: "Do you worry that Paul Ryan's controversial Medicare plan will hurt the campaign with independents? No. President Obama is the one who should be worried, because he has cut $700 BILLION from Medicare to pay for Obamacare, and put in place a panel of Washington bureaucrats to make decisions about what kind of care seniors will receive under Medicare. Mitt Romney and Paul Ryan have a bipartisan plan to strengthen Medicare by giving future seniors the choice between traditional Medicare and a variety of private plans. They are committed to ensuring that Medicare remains strong, not just for today's seniors, but for tomorrow's seniors as well."

The Washington Post's Ezra Klein, though, points out, "It’s not just that Romney now has to defend Ryan’s budget. To some degree, that was always going to be true. What he will now have to defend is everything else Ryan has proposed. Ryan was, for instance, the key House backer of Social Security privatization. His bill, The Social Security Personal Savings Guarantee and Prosperity Act of 2005, was so aggressive that it was rejected by the Bush administration. Now it’s Romney’s bill to defend. In Florida."