The House vote today that’s expected to pass Paul Ryan’s proposal to end Medicare as we know it will be looked back on as the day the GOP lost the House, DCCC chair Steve Israel vowed to me in an interview moments ago.

“When we win back the majority, people will look back at this vote as a defining one that secured the majority for Democrats,” Israel said.

Israel said that Dems plan to use the Medicare vote today to go on the offensive against Republicans from now all the way until Election Day 2012. Crucially, Israel said it would be used in every district, even ones that are marginal or conservative — suggesting that on Medicare at least, Dems are hoping to maintain a united national front, rather than letting the messsage be watered down in conservative districts that may be more receptive to GOP messages about fiscal conservatism.

“All the polling tells us the same thing,” Israel said. “Voting to terminate Medicare is a bad idea politically in every district.. Republicans oppose it. Democrats oppose it. And Independents oppose it.”

Israel said the party was going to use the Medicare vote to hone a national message based on “choices” that ties the GOP drive to end Medicare as we know it to the desire for tax cuts for the rich.

“We’re creating a national framework on choices,” Israel said. “The choice I hope our members talk about at home is a budget that gives you a $100,000 tax cut if you earn over $1 million a year, and a $12,000 cost increase if you’re a senior on Medicare. That contrast is very compelling.”

Pushed to say whether he thought that if Obama agrees to any cuts or changes to Medicare in further negotiations it could muddle the party’s message and prevent Dems from drawing a strong contrast, Israel insisted negotiations with Republicans wouldn’t hurt.

“We hav a responsibility to engage responsibily with Republicans on improvements to Medicare,” Israel said. “But Republicans haven’t offered improvements. They’ve launched right to the termination of Medicare. That’s the basic difference between them and us and we intend to point that out aggressively.”

Republicans say that Dems in marginal districts will be in political danger if they support Obama’s call for higher taxes on the rich, because they’ll be able to paint Dems as tax and spend liberals.

Pushed on whether he agrees with this view, Israel insisted that Dems in conservative districts would not let this dictate their playbook. He said they’d be on solid political ground calling for high end tax hikes by tying it to the GOP drive to end Medicare.

“I don’t know of any marginal district in America where people would support a budget that gives people who make over $1 million a $100,000 tax cut and people on Medicare an additional $12,000 medical cost increase,” Israel said.

UPDATE: It’s worth noting that non-partisan observer Charlie Cook recently came close to endorsing Israel’s view, claiming that undertaking a major overhaul of Medicare could be “little short of suicidal” for the GOP. And Republican strategists have also expressed serious worry about the political risks involved.

UPDATE II: NRCC spokesman Paul Lindsay responds:

“If there is one thing Steve Israel is faithful to, it is his party’s shameless scare tactics intended to cover up the Democrats’ plan to watch Medicare die a painful death. House Republicans think that is an unacceptable option for America’s seniors, which is why they have proposed a solution to strengthen and save Medicare. Israel may be very confident of his goal to make Nancy Pelosi the Speaker again, but the nightmare of her job-destroying reign in Washington is still haunting middle-class families who are determined to never see her in power again.”

UPDATE III: The House has now passed the measure along party lines, with only four Republicans voting against it. Israel’s prediction will be put to the test...