New data today on Medicare costs, nicely presented by Sarah Kliff, offer a good reminder that there are two completely different discussions these days about Medicare and deficits — and only one of them is reality-based.

In the story you’ll hear most often, there’s a major budget crisis because “entitlements” are growing out of control — and that Republicans have been fighting to reform entitlements, but Democrats refuse to touch them. One version of that story has Republicans equally guilty about (what are said to be) exploding deficits because they refuse to touch revenue; the most generous version even admits that President Obama has offered to cut benefits (by using a different inflation measure) in return for revenue, and debates to what extent that offer — and therefore Democratic willingness to ever touch entitlements — is honest.

But in the real world, there’s a completely different story. In the real world, Democrats passed the Affordable Care Act in 2010, and it contained all sorts of serious reforms intended to cut Medicare costs. And in that real world, there’s evidence — not conclusive evidence, but evidence nonetheless — that those reforms are beginning to work. In this story, Democrats already acted, over the objections of every Republican, to reform the one entitlement program that had been the biggest problem.

Indeed, in this story, Republicans have repeatedly attacked each of these cuts. People have finally noticed that Republicans have constantly attacked the immediate Medicare cuts included in the ACA while still attacking Democrats for those cuts, but that’s only the beginning. Remember that Republicans are still attacking the Independent Payment Advisory Board, for example.

Meanwhile, that first story? Yes, House Republican budgets have been calling for massive Medicare reforms. For years, now, really. But as far as I can see, even that is basically fantasy. Has the House actually passed a bill to implement Paul Ryan’s vision? Nope. Is there even a bill? Are there any hearings about how the plan would actually work in the real world? It’s pretty easy to claim to support a massive reform that would work out well for everyone…but it’s even easier if you keep it all at the purely rhetorical level.

The bottom line? It’s just absolutely insane — fully immersed in fantasy — to claim that Obama and the Democrats won’t touch entitlements. Especially Medicare. One can certainly argue that Obamacare didn’t cut enough, made the wrong cuts, won’t work, or is a bad idea even if it works…but no one should pretend that it doesn’t exist.

That’s the reality-based story of Medicare, entitlements and the budget. The one that you’ve been hearing? That’s almost pure fantasy.