There’s probably no organization in Washington that has been more aggressive in making the case that Republicans want to “end Medicare” than the DCCC. And so, when PolitiFact declared that claim its “Lie of the Year” today, Republicans suggested that the DCCC might now have a tough time making it in ads against vulnerable House Republicans who voted for the Paul Ryan plan.

But Dems aren’t backing away from the claim. Asked for comment on PolitiFact’s designation, DCCC spokesman Jesse Ferguson emailed:

“Politifact doesn’t have its facts straight on the Republican plan to end Medicare. As Noble Prize-winning economist Paul Krugman said today, the House Republican scheme ends Medicare and leaves seniors with a voucher and no guarantee they can afford health care costs that would double.”

Oh, well. Looks like the DCCC told PolitiFact’s “Lie of the Year” two more times in just one statement.

PolitiFact’s assertion has been widely pilloried by liberal writers. Krugman, Steve Benen, Igor Volsky, Jamelle Bouie and David Dayen all argue that the claim that Republicans want to “end Medicare” is true. Jonathan Chait argues that it’s ultimately a matter of opinion. Kevin Drum dissents, insisting that ultimately the Dem claim was designed to mislead.

My view is that it’s probably marginally more advisable to say that Republicans tried to end Medicare as we know it, rather than to say they tried to end it, because that leaves no ambiguity about the point Dems are trying to make.

That said, I think there’s still a way of persuading Politifact that they erred. Here’s why: Even if you agree with PolitiFact that the GOP plan wouldn’t have “ended” Medicare, the Dem claim that this is the case still can’t be shown to be a “lie.” That’s because this disagreement ultimately comes down to differing interpretations of known facts — and not to a difference over the facts themselves.

The GOP plan would turn a fee-for-service program which guarantees essential care to all seniors into one in which seniors get something approximating vouchers to pay for private insurance. Under the Ryan plan there would be no defined benefits, and seniors would pay more for their insurance over time.

If you define Medicare by its traditional function — guaranteeing coverage via single payer — then the GOP plan would end Medicare. But if you define Medicare more loosely, as a program designed to make sure seniors get some form of coverage — and see the single-payer and guaranteed-essential-care elements as simply means to that general end that are not central to the program’s reason for being — then the GOP plan would not completely end Medicare.

It seems clear that the former definition is far more in sync with the spirit of the program, as it was originally conceived. But the key point is that even if you agree with the latter interpretation, the Dem claim still isn’t a “lie.” It’s a difference of interpretation. You can’t prove that the former definition of what makes Medicare what we think of as Medicare is inaccurate or even all that unreasonable. And if you can’t disprove the Dem definition of Medicare, which is the logical basis for the claim that the GOP would end it, then you can’t prove definitively that Dems are “lying.”

You can argue that their definition of the program and their resultant interpretation of the facts are wrongheaded. But you can’t prove that they’re wrong. So there’s no basis for claiming definitively that Dems told a factual falsehood, let alone the “Lie of the Year.”

But since Dems are brushing off Politifact’s finding, all this may be moot in any case.