WASHINGTON - Social Security is on the table.

Liberals do not like it, but recalculating the cost-of-living adjustments in Social Security benefits is part of the talks over the year-end fiscal cliff and may become to Democrats what raising taxes is to Republicans: a powder keg.

Averting a cliff dive next week may well depend on the parties stomaching both possibilities.

When Democrats talk about Social Security, they sound a lot like their Republican colleagues talking about tax rates.

"It's certainly not something that is acceptable to me," Rep. Hank Johnson, a Georgia Democrat, said last week when asked about "chained CPI."

The term refers to changing how inflation is calculated, affecting a slew of policies including Social Security benefits and marginal tax rates. The government currently uses the consumer price index, based on a fixed set of goods. A "chained" consumer price index takes into account the fact that people are likely to substitute cheaper goods for more expensive ones as prices shift, and many economists argue it is a more effective measure of inflation.

And in a town looking for ways to save money, it's a bonanza: The Committee for a Responsible Federal Budget, a group pushing the chained CPI as part of a budget deal that follows the Bowles-Simpson fiscal commission's outline, estimates the switch would save $236 billion over the next decade if implemented in 2014.

Sacrosanct to many

But much of that money comes out of the pockets of senior citizens by shaving their benefit increases. Even if this is "fairer," many Democrats object to any serious tinkering with the sacrosanct, FDR-era program.

They argue that any savings ought to go to the fast-draining Social Security trust fund rather than deficit reduction.

Johnson said both the Congressional Black Caucus and Congressional Progressive Caucus oppose chained CPI. Rep. John Lewis, D-Ga., issued a statement complaining that "some are using Social Security as a carrot to get a deal."

That "some" reportedly includes President Obama, though Lewis was not naming names. Obama is reported to have floated the idea during last year's debt-ceiling standoff with House Speaker John Boehner, and it has re-emerged this time as a way to wring savings from entitlement programs.

While many Democrats seem to be drawing a red line around Social Security and liberal groups are vowing to hold their feet to the fire Grover Norquist-style, some Democrats are leaving wiggle room.

Nancy Pelosi said last week that she feels chained CPI "strengthens" Social Security, offering a window into the thinking of a woman who has proved to be more effective at counting votes than Boehner.