Liberals on Tuesday blasted the White House's latest fiscal-cliff proposal as a cut to Social Security benefits.

Perhaps it's a sign that President Obama and congressional Republicans have moved closer to a deal.

GOP House Speaker John Boehner had suggested tying Social Security and other benefits to to a "chained CPI" (Consumer Price Index), which could slow benefit increases that are tied to inflation. On Monday night, the White House countered with an offer that included what it called a "superlative CPI," which would cut less money over 10 years and would exempt the neediest beneficiaries from a CPI change.

The liberal Progressive Change Campaign Committee (PCCC) on Tuesday morning circulated criticism from a handful of progressive players, signifying that politicians and interest groups on the left, who have decried any cuts to Social Security or Medicare, will coordinate at least some degree of pushback against this movement toward a compromise.

"Everyone has a grandparent, a friend or a neighbor who relies on the Social Security benefits they earned to pay for medical care, food and housing. A move towards chained CPI would be a long-term benefit cut for every single person who receives a Social Security check," said House Progressive Caucus co-chair Keith Ellison, D-Minn., citing estimates that a chained CPI (as included in the GOP's proposal) would cost beneficiaries thousands over 15 years.

"The average Social Security recipient rakes in a whopping $13,000 a year. If we pass chained CPI, projected annual cuts for a typical retiree would be about $560 a year by age 75, $984 a year by age 85 and $1,400 a year by age 95," said the Progressive Caucus's other co-chair, Rep. Raul Grijalva, D-Ariz.

"MoveOn members overwhelmingly oppose cuts to Social Security, Medicare, and Medicaid benefits, and they've made clear that they would see any fiscal agreement that cuts such benefits as a betrayal that sells out working and middle class families - whether the cuts come via a chained CPI, increased Medicare eligibility age, or in some other form," said MoveOn.org Executive Director Justin Ruben. "If such a deal were proposed by the President and Speaker, MoveOn members would expect every Senate and House Democrat to do everything in their power to block it."

"This proposed deal will cut Social Security benefits. Any deal that cuts Social Security, Medicare, or Medicaid benefits is unacceptable - and progressive organizations join with the overwhelming majority of Americans who oppose it," said PCCC co-founder Stephanie Taylor.

And a progressive member of the Senate leadership, Majority Whip Dick Durbin, D-Ill., has also criticized the GOP's CPI-change proposal.

"We ought to deal with Social Security in a separate conversation that is not part of deficit reduction," Durbin told The Washington Post's Greg Sargent.

"The Speaker and many of his Republican friends are hell bent on Chained CPI," Durbin told Sargent. "It may be part of an overall solution [later] but to do it at this stage is the wrong way to go."

In late November, Durbin warned liberals at the Center for American Progress that they'll need to entertain deficit-reduction plans other than taxing the rich. At the moment, it appears the progressive voice in Democratic Senate leadership is okay with a CPI change eventually - just not now.