Here’s a good test case for how Dems will attack vulnerable House GOPers over Medicare this year — even though Politifact has declared the core Dem message that Republicans would “end Medicare” the “Lie of the Year.”

Stick with me here. This is important.

The other day, the House Majority PAC — which plans to raise and spend millions to elect Dems to the House — went up with a new ad attacking Iowa GOP Rep. Tom Latham, who’s facing a tough challenge from Democrat Leonard Boswell in a newly redrawn, highly competitive district. The ad accused Latham of voting to “essentially end Medicare.”

The Republican then responded with his own ad citing the PolitiFact finding. It insisted that “independent fact checkers” call the attack in the earlier ad “the Lie of the Year.” This is something you can expect lots more of; the Politifact ruling is likely to be heavily featured in GOP ads across the country.

And so, the House Majority PAC is back with still another ad doubling down on the claim that the GOPer voted to “essentially end Medicare,” and asserting that the claim is 100 percent true:

Democratic operatives are closely monitoring this ad to see how it fares; they see it as a template for future spots to rebut the inevitable GOP ads citing the Politifact finding. The stakes are high: Paul Ryan will again push a version of his Medicare plan, and Dems will make attacks on it central in races across the country.

A side irony: The claim in the Dem ads that Republicans voted to “essentially end Medicare” was actually not declared the “Lie of the Year.” That was bestowed on the claim that GOPers voted to “end Medicare” — without the “essentially.” The claim that the Ryan plan would “essentially end Medicare” actually comes from the Wall Street Journal. Yet Repulicans will likely continue to say that Politifact declared this a lie.

Meanwhile, the Republican spot above that cited the Politifact finding also accuses Democrats of being the only ones to cut Medicare, claiming $500 billion in cuts. As it happens, Politifact has declared that claim false.

Either way, the assertion that Republicans voted to end Medicare — or essentially end Medicare, or end Medicare as we know it — will live on.