Over the weekend, GOP Rep. Paul Ryan confirmed that the House Republican budget would again contain key elements of his plan to transform Medicare — even though some polls have shown the idea to be deeply unpopular and Dems have vowed to run on it in 2012.

Asked by The New York Times whether he intended to push similar changes to Medicare again this year, Ryan replied: “Yes, absolutely.”

Now the Democratic Congressional Campaign Committee is set to go on the offensive on the issue in the increasingly close battle for the House — and it’s very possible the issue could have a real impact on the presidential race.

The DCCC will go out today with what it’s calling a “Groundhog Day Alert” in the districts of some 70 vulnerable House Republicans, reminding voters of their last vote on Medicare and warning of the next one to come. Here’s what the alert in the district of Rep. Dan Benishek of Michigan says:

“Michigan voters don’t need a groundhog to come out of the hole in order to tell them how this will end: Voters will reject Dan Benishek putting the ultra wealthy ahead of seniors once again. Even though voters already rejected House Republicans plan to end Medicare, this Groundhog Day Republicans like Benishek are resurrecting their plan to protect billionaires and Big Oil, while leaving seniors out in the cold. It’s the same thing again from Dan Benishek — double health care costs for Michigan seniors, more tax breaks for the ultra wealthy.”

DCCC chair Steve Israel has reportedly instructed House Dem candidates to be relentless in stressing the GOP position on Medicare, to make it a “defining issue in the 2012 elections.” A recent poll by the Dem firm Democracy Corps found that the Dem message — that House Republicans voted to “end Medicare as we know it” — tests well, with 77 percent in 60 House GOP districts saying it raises serious doubts about incumbents.

The Ryan Medicare plan has become a cause celebre on the right. And so Dems are hoping to use its return to paint the House GOP as AWOL on jobs and still in the grip of its Tea Party wing — after the Tea Party caucus helped engineer the debt ceiling and payroll tax cut debacles that helped drag down the GOP’s (and Congress’s) approval ratings to historic lows. Israel has been unwilling to predict that Dems will recapture the House, and House Republicans have been working hard to signal seriousness about jobs by, among other things, rolling out a plan yesterday to cut small business taxes.

But Medicare may again loom large, and one big question is whether it will prove a drag on presumtive GOP nominee Mitt Romney. The fierce competition with Newt Gingrich forced Romney to fully embrace the Ryan Medicare plan, in order to get around to Gingrich’s right. Dems know that it’s crucial that they prevent Romney from achieving separation from the unpopular GOP Congress — and his embrace of the Ryan plan is perhaps the number one shackle Dems will use to attach Romney to the House GOP. How much this will ultimately matter in the general election is an open question, but a rerun of the debate over Ryan and Medicare could make this task that much easier for Dems.