I've got a modest proposal: You're not allowed to demand a "serious conversation" over Medicare unless you can answer these three questions:

1) Mitt Romney says that "unlike the current president who has cut Medicare funding by $700 billion. We will preserve and protect Medicare." What happens to those cuts in the Ryan budget?

2) What is the growth rate of Medicare under the Ryan budget?

3) What is the growth rate of Medicare under the Obama budget?

The answers to these questions are, in order, "it keeps them," "GDP+0.5%," and "GDP+0.5%."

Let's be very clear on what that means: Ryan's budget — which Romney has endorsed — keeps Obama's cuts to Medicare, and both Ryan and Obama envision the same long-term spending path for Medicare. The difference between the two campaigns is not in how much they cut Medicare, but in how they cut Medicare.

This bus always believes in America. But it only occasionally believes in the Democrats' Medicare plan. (Linda Davidson -- The Washington Post)

This brings us to the big myth of this campaign, or at least of this particular conversation: That Republicans, but not Democrats, have a plan to cut Medicare costs. As Ryan pointedly put it in his first speech as Romney's vice-presidential pick, "We won't duck the tough issues. We will lead!"

Obama's Medicare reform plan isn't that hard to find. It's largely in Title III of The Patient Protection and Affordable Care Act. The basic strategy has three components: First, figure out what "quality" in health care is. Second, figure out how to pay for quality rather than paying for volume. Third, make it easier for Medicare to quickly update itself to reflect both advances in knowledge about what quality is and how to pay for it.

And so, in Title III, you'll find dozens of different efforts to achieve these goals. The most famous of them is Section 3403, which establishes the Independent Payment Advisory Board (IPAB). But there's also Section 3021, which creates the Center for Medicare and Medicaid Innovation, and Section 3025, which cuts hospital reimbursements if too many of their patients are readmitted, and Section 3001, which establishes value-based purchasing for hospital services, and Section 3015, which collects data on quality, and Section 3502, which advances the medical home model.

Some of the efforts are outside Title III. The Patient-Centered Outcomes Research Institute is actually in Title VI of the law. And then there are the subsequent reforms the administration has proposed to save more money. Those can be found on pages 33-37 of the president's 2013 budget proposal. They include expanding IPAB's mandate such that it can change Medicare's benefit package and setting a growth cap on Medicare of GDP+0.5 percentage points -- which is, by the way, the same growth cap that Rep. Paul Ryan imposes in the latest iteration of his budget.

As for Romney's plan? Well, it's 902 words long, and basically sketches a less-detailed version of the plan Ryan released in his 2013 budget proposal (which is, for the record, much more moderate than the plan in his 2012 budget).

Romney would give Medicare beneficiaries a voucher permitting them to choose between traditional Medicare and private plans. Romney's people tell me his plan will use competitive bidding, in which the value of the voucher is tied to the lowest-cost (or, in some versions, second-lowest cost) plan. If beneficiaries want a more expensive plan, they'll have to pay the difference out of pocket. On his Web site, however, it just says that Romney "is exploring different options for ensuring that future seniors receive the premium support they need while also ensuring that competitive pressures encourage providers to improve quality and control cost."

Which is fine. I actually think that on Medicare, unlike on other issues, Romney has provided an acceptable level of detail to evaluate where he'd like to take the system. But that's not the same as saying it's detailed.

These plans get at the basic disagreement between Democrats and Republicans on Medicare. Democrats believe the best way to reform Medicare is to leave the program intact but vastly strengthen its ability to pay for quality. Republicans believe the best way to reform Medicare is to fracture the system between private plans and traditional Medicare and let competition do its work.

It's worth saying there's no particularly good evidence for either option. Competition hasn't worked very well in the health-care system. Indeed, Medicare currently includes private options through the Medicare Advantage program. The idea was these private, managed-care alternatives would be cheaper than traditional Medicare. As it turned out, they ended up costing about 20 percent more.

As for the pay-for-quality revolution that the Obama administration envisions, that hasn't been proven at Medicare's scale, either.

Both Ryan and Obama — but not Romney — have proposed to back up their promises with an enforceable cap on the program's future growth. Whether future Congresses would actually enforce such caps is, of course, an open question.

So there's a conflict of policy visions. But it's simply a conservative myth that the White House hasn't put forward a Medicare reform plan. What that line really means is that White House hasn't put forward some variant of Ryan's plan, which in many Republican circles, has come to be seen as the only policy change that counts as "entitlement reform."

But Obama's plan is, without doubt, far more detailed than anything Romney has put forward, and Republicans are well aware of its existence. One Republican accused Obama of a "bureaucratic approach to controlling Medicare costs" which "empowers a board of 15 unelected officials — the Independent Payment Advisory Board, or IPAB — to hold the growth of Medicare spending." He said the cuts would be so severe that they "would simply drive Medicare providers out of business, resulting in harsh disruptions and denied care for seniors.”

That Republican? Paul Ryan.