In December, Max Richtman attended a meeting at the White House with other progressive groups during the negotiations to avert the fiscal cliff.

As the president and CEO of the National Committee to Preserve Social Security and Medicare, Richtman only wanted to tell President Barack Obama one thing: No cuts in either of the two programs.

"He told me, 'We agree with you,'" Richtman said today, recalling the meeting. "Well, I guess something has changed since then."

What's changed is that Obama has officially embraced a proposal to cut Social Security benefits known as "chained CPI," which recalculates the growth of benefits by using an index that doesn't rise as quickly as inflation.

While the administration is portraying chained CPI as a concession to find compromise with Republicans, the proposal has infuriated Obama's liberal base.

And for many of these progressives, it confirms concerns that they have harbored for some time.

Eric Kingson, co-chair of the Strengthen Social Security Coalition and a professor at Syracuse University, told Business Insider Wednesday that Obama has "waffled" on Social Security since taking office in 2009 — despite a 2008 speech to the AARP convention in which then-Senator Obama criticized the same plan he's proposing now.

"He has never been forthright about this issue," Kingson said. "He has always been reticent to speak out about protecting Social Security."

Kingson suggested that the Obama administration was being "disingenuous" about the actual scope of the cuts, using Washington-speak to refer to it as a "tweak" or a simple change in the way benefits are calculated.

But he has long suspected Obama has wanted to slash Social Security benefits.

"I really think he believes that for whatever reason, this program needs to be cut," Kingson said. "But what he's doing is disrespectful — it's undermining the institution."

Dean Baker, the co-director of the Center for Economic and Policy Research, said he believes Obama is offering the proposal in an attempt to be "serious" and appeal to Beltway types who crave bipartisanship. But he thinks Obama has the wrong definition of being serious.

"You piss on the people who care about Social Security, then you're serious," Baker said.