A RARE UNITING MOMENT FOR DEMOCRATS…. In recent memory, there’s really only one high-profile policy fight that united every faction of the American center-left — George W. Bush’s 2005 push to privatize Social Security.

Looking back, it was actually pretty impressive. The media was generally inclined to praise the effort — ending the traditional Social Security system is apparently evidence of “seriousness” — but this was one of those rare moments in which progressive wonks, lefty activists, and Democrats at every level were effectively saying the same thing, at the same time, for the same reason.

Incidentally, they won. The public hated the Bush plan; Republicans abandoned it; and the proposal withered on the vine, failing to even get a vote in Congress. It all happened rather organically, too — there was no top-down model, since there were no progressives in a position of power at the time.

There’s no reason we can’t see something similar this year, in response to the House Republican budget plan. Bush wanted to eliminate Social Security, and Paul Ryan & Co. want to eliminate Medicare. These are not only both pillars of American public life, but they’re also both pillars of the Democratic tradition.

With that in mind, I was delighted to see a full-throated condemnation from Senate Finance Committee Chairman Max Baucus (D-Mont.) — not exactly a raging liberal from a “blue” state — in response to yesterday’s announcement from the House GOP.

“Independent experts agree the House Plan would make deep cuts to the Medicare benefits seniors count on,” said Baucus. “It would end Medicare as we know it and funnel Medicare dollars directly into private insurance companies’ pockets. Under the House plan, seniors’ coverage would be cut drastically, benefits would no longer be guaranteed and seniors’ costs would skyrocket. We can’t allow the House to balance the budget on the backs of seniors and we won’t — not on my watch.”

It was soon followed by a statement from Senate Budget Committee Chairman Kent Conrad (D-N.D.) — again, not exactly a traditional progressive champion — who also wasn’t impressed.

“Representative Ryan’s proposal is partisan and ideological. He provides dramatic tax cuts for the wealthiest, financed by draconian reductions in Medicare and Medicaid. His proposals are unreasonable and unsustainable. His plan is most troubling because it lacks balance.”

Regrettably, Conrad’s statement included praise for the Simpson/Bowles Fiscal Commission plan, but the point is, the senator immediately realized the House Republican plan deserved to be rejected out of hand, and in particular, Conrad offered a strong defense of Medicare.

Brian Beutler added this morning, “A funny thing happened on the way to a government shutdown. Democrats got on message about the House Republicans’ other, bigger budget, which creates a policy blueprint for the next decade. That message? The GOP plan to end Medicare and hack away at Medicaid is a non-starter. This came from top Democrats across the political spectrum.”

Uniting Democrats and progressive activists is always difficult, but there’s ample reason to believe Paul Ryan has presented a unique opportunity. It happened in 2005, and if the left is smart, it’ll happen in 2011.

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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.