HOW TO DEFEND THE INDEFENSIBLE…. Sen. Marco Rubio (R-Fla.) made his “Meet the Press” debut the other day, and was asked about his support for the Republican plan to end Medicare. Given the number of retirees in Florida, Rubio’s position is of particular interest.

He responded that the GOP proposal “doesn’t cut Medicare,” adding, “The only people in this town that have voted to cut Medicare spending are the people who voted in favor of Obamacare. That’s a fact.”

Except, that’s not a fact at all. Jonathan Cohn explains today, “It’s becoming pretty clear how Republicans plan to defend their budget. They’re going to lie about it.”

Yes, the Affordable Care Act reduces spending on Medicare. But it does so gradually, by establishing a long-term goal of allowing the program to grow at the same rate of gross domestic product plus one additional percentage points — that is, GDP+1. And it’s a goal in the truest sense of the word. If the program’s starts growing at a faster pace, there are mechanisms to slow it down but not necessarily to get it all the way back to GDP+1.

The Republican budget, by contrast, would hold the cost growth of Medicare to the consumer price index, or CPI. CPI grows considerably slower than GDP, let alone GDP+1, so that’s no small thing. The Republican budget would also enforce this target rigidly, by handing seniors vouchers whose value is set by a fixed, pre-determined formula. At the same time, the Republican budget would dramatically reduce the federal investment in Medicaid, on which so many of the elderly rely for supplemental coverage and/or long-term care, particularly nursing homes.

Overall, according to the Congressional Budget Office, the difference between the two plans goes from about 1 percentage point of GDP in 2022 to between 7 and 9 percentage points of GDP by 2050.

In other words, Rubio’s on-air response wasn’t even close to being accurate. I’m sure the right liked it — the senator was rehashing misleading arguments from 2010, and got to say “Obamacare” a bunch of times — but as Cohn noted, Rubio’s answer was “pretty much the opposite of the truth.”

It’s likely Rubio didn’t know he was deceiving a national television audience. He was no doubt prepped on what to say, and the senator, who doesn’t appear to be especially bright, repeated the same phrases over and over again in the interview, reinforcing the notion that he was clinging to his talking points with all of his might.

Or maybe Rubio is a secret wonk and knew exactly what he was talking about, in which case he was shamelessly lying through his teeth.

But the one thing I’d add to Cohn’s report, which is worth reading in full, is how “Meet the Press” host David Gregory responded to Rubio’s lying. There was some pushback, but it was mild and superficial, and viewers likely had no idea the senator’s comments were completely wrong. Indeed, the transcript offers a script for how Republicans should lie their way through the debate: say the plan to end Medicare actually “saves” the program, and if pressed, say Democrats don’t have a plan of their own.

This is why we can’t have nice things.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.