In an interview with me today, Senator Bernie Sanders said that progressive Democratic Senators should be prepared to band together to block any “grand bargain” that includes cuts to entitlement benefits — and even hinted that he and others might filibuster such a deal, if necessary.

As talk increases of White House outreach to Republicans in search of a big deal to replace the sequester, a question has presented itself. Is there any other realistic endgame in this battle, aside from either continued sequestration or a deal to avert it, in which Republicans agree to new revenues in exchange for entitlement cuts, including Chained CPI for Social Security and Medicare means testing? Republicans will never agree to repeal the sequester. So realistically, isn’t the choice between a deal or sequestration limbo, with future budgets configured around lower spending levels, damaging the economy?

Sanders insists to me that this framing — which I had adopted — is the wrong way to look at this fight. Instead, he says Dems must build a coalition to leverage public opinion to force Republicans to accept a resolution that combines judicious spending cuts with new revenues from the rich and corporations — while preserving entitlement benefits.

“It’s a question of making Republicans an offer they can’t refuse,” Sanders tells me. “Their position is no more revenues. You and I know that is not the position of the American people. One in four corporations doesn’t pay any taxes. What Democrats and progressives should say is, `Sorry, we’re not going to balance the budget on the backs of the vulnerable.'” Sanders described the idea of cutting education, Social Security, Medicare and veterans’ benefits as an “obscenity.”

But Republicans don’t care about national public opinion on these matters, I pointed out to Sanders. What if they just say, “we’re sticking with the sequester”? I pressed Sanders on what should happen then. He reiterated that Democrats must not get drawn into this framing, that they should build a coalition — of seniors’ groups, veterans’ groups, progressive groups, etc. — to force the Republicans’ hand, and that they should “go around the country talking about this issue.”

“The alternative is not to go into a back room and negotiate with Boehner; it’s to make our case to the American people,” Sanders said. “I don’t believe there’s a red state in America where people believe you should cut Medicare, Social Security and veterans’ benefits rather than doing away with corporate tax loopholes.”

I asked Sanders if he would filibuster any grand bargain that cuts entitlement benefits. “It’s more than just the filibuster,” he said. “That’s a one day tactic. This is about rallying the American people and winning.” He predicted liberals in the Senate (Jeff Merkley, Sherrod Brown, and Elizabeth Warren come to mind) would likely band together to adopt a range of tactics to block such a grand bargain. “Filibustering may be part of it,” he said.

It’s still unclear to me what the endgame would look like if liberals stick with such a strategy. Republicans could simply continue to support indefinite sequestration rather than agree to anything at all, let alone a deal that includes new revenues but no entitlement cuts. Or if the White House does strike a grand bargain, liberal Dems may ultimately cave and support it. Or if a deal is reached in the Senate, it could pass without liberals. However unclear the way foward remains, it’s undeniably good for progressive Senators to be out there defining the liberal position in the debate in as high-profile a way as possible.