There is a pattern to Romney's campaign of lies: accuse President Obama of the very things candidate Romney is doing. This "I know you are but what am I" tactic, in PR-speak, "provides cover." And this one is a big one, with Romney accusing Obama of cutting Medicare. Wow.
A prominent feature of the "Ryan Plan" is the virtual elimination of Medicare. Ryan guts the Medicare program, turns it into a voucher plan to buy private insurance, and doesn't give you enough money for adequate insurance. But it's still named "Medicare," so the "fact-checkers" have a way to call Democrats liars for saying the Ryan Plan eliminates Medicare. Also, it only eliminates Medicare for people currently under 55, so you seniors will "be OK."
Mitt Romney chose Paul "Ryan Plan" Ryan to be his running mate, because he absolutely needs to keep the Ayn Randian component of the "base" of the Republican Party enthused. (The "Southern Strategy" component is under control, Drudge Report is running with 8 stories about "black mobs" attacking white women, and 5 stories about the "New Black Panther Party" - one guy - intimidating the good white voters by standing outside one polling place.)
The problem with choosing Paul Ryan as his running mate is that it hangs the Ryan Plan around his neck. Medicare is enormously popular, and for good reason. "Fact-checkers" are doing everything they can to provide cover for the Ryan Plan -- after all, it's still named "Medicare" -- but people just aren't that stupid. At least not enough people. So Mitt Romney has a terrible problem to solve.
Mitt Romney has a tried-and-true solution to the problem of the public getting upset at something he is proposing -- tell the public the other guy is the one proposing it! Talk about "muddying the waters."
Seriously, when you steal a cookie from the cookie jar, accuse your brother of stealing the cookie before he gets a chance to snitch on you. Then, when he snitches, he will sound like he's the one covering for what he did. "I didn't steal the cookie, Mitt did!"
Here is FOX News, helping provide cover for Romney using the old "they both do it" and "one side says the world is flat, the other side says it is round" horse-race reproting method, Debate joined on Medicare; Romney, Obama go at it 
Mitt Romney accused President Barack Obama in person and in TV advertising Tuesday of cutting Medicare "to pay for Obamacare," launching a strong counterattack to Democratic charges that he and running mate Paul Ryan would radically remake the popular health care program that serves tens of millions of seniors.
The charge drew a blistering response from Obama's campaign, which labeled the ad dishonest and hypocritical.
Obama "has taken $716 billion out of the Medicare trust fund. He's raided that trust fund," Romney said at a campaign stop in Beallsville, Ohio, as he neared the end of a multi-state bus trip punctuated by his weekend selection of a ticket mate.
The Washington Post has an analysis  of where, how and why the Affordable Care Act - "Obamacare" - cuts Medicare.
The Affordable Care Act ... tethers reimbursement levels to the quality of care administered, and patient satisfaction.
... The health law changed how Medicare calculates what they get reimbursed for various services, slightly lowering their rates over time. Hospitals agreed to these cuts because they knew, at the same time, they would likely see an influx of paying patients with the Affordable Care Act’s insurance expansion.
... “It’s worth noting that there’s one area these cuts don’t touch: Medicare benefits. The Affordable Care Act rolls back payment rates for hospitals and insurers. It does not, however, change the basket of benefits that patients have access to.”
Ryan and most Republicans, by the way, voted for exactly the same set of "cuts" in Medicare... But who's counting?
Note - see also:
Terrance Heath: The GOP Still Wants to Gut Medicaid 
Nancy Altman: How The Ryan Plan Threatens Middle-Class Retirement Security