Breaking down the basics of the “fiscal cliff.” (The Washington Post)

There is no deal yet to avert the year-end “fiscal cliff.”

But that hasn’t stopped the pressure from beginning to build to reject the not-yet-a-deal, as potential concessions offered by House Speaker John A. Boehner (R-Ohio) and President Obama in private weekend talks have begun to emerge, setting off anxiety in activist groups on the left and right.

The anger being brought to bear against a nascent budget framework helps illustrate how hard it has been to get a bipartisan deal on deficit reduction in recent years.

The coming days will be critical, determining whether GOP rank-and-file balk at raising taxes — Boehner, sources say, has indicated a willingness to allow tax rates to rise at least for those making more than a million dollars a year.

Democratic leaders will also be feeling out liberals to see whether they will vote for entitlement cuts as part of a deficit reduction deal.

Post reporter Paul Kane stops by to give us the latest developments in the talks between House Speaker Boehner and President Obama and if a deal looks likely this week. (The Fold/The Washington Post)

So far, the rhetoric from the right has been tougher for Boehner, as anti-tax groups have swung into gear, urging conservatives to reject any arrangement that includes new tax dollars and accusing the House speaker of capitulating in a two-decade battle between the parties over taxes.

“The Republican Party can’t be a party that stands for increasing taxes,” said Michael Needham, chief executive of the Heritage Action for America. “The country needs a contrast. . . . He’s certainly not providing that kind of contrast.”

Needham said he was “horrified” to read reports that Boehner had offered a deal with $1 trillion in new revenue and said he hopes conservatives rise up in revolt at a closed-door meeting of the House GOP on Tuesday and threaten Boehner’s speakership if he does not respond.

“It’d be pretty disappointing if a Republican conference meeting happens and there’s not a backlash,” Needham said.

Club for Growth President Chris Chocola, meanwhile, criticized Boehner for indicating a willingness to raise the debt ceiling for a year as part of a grand bargain that reduced the deficit by at least an equal amount.

“Raising tax rates is anti-growth and raising the debt ceiling is pro-government growth — and this is the Republican position?” he said in a statement.

But Democrats will not find it any easier to accept a deal along the lines of what has been discussed between Boehner and Obama.

The AARP has been running ads, nationally and in Washington, urging Congress to resist proposals to raise the Medicare retirement age or changing the definition of inflation to reduce annual Social Security cost-of-living increases.

“Nobody has said to us, don’t worry,” said David Certner, legislative policy director for the AARP. “Those things are still on the table, and we are still concerned about the fact that they are on the table.”

Democrats will find themselves under particular pressure not to offer significant entitlement cuts in exchange for allowing tax rates to revert to their Bill Clinton-era level for only the super wealthy, those making more than a million a year.

Late Monday, the activist group warned Democratic lawmakers that the group would consider a Social Security benefit cut of the kind offered by Obama in talks Monday to be “a betrayal that sells out working and middle class families.”

“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,” according to a group statement.

Obama has said he wants to allow tax breaks enacted under President George W. Bush to expire for those making more than $250,000. As negotiations continue, Obama on Monday offered to raise that threshold to $400,000.

Boehner’s concession “does not come close to raising the revenue needed to reduce the deficit and rebuild the economy,” said Frank Clemente, campaign manager for Americans for Tax Fairness.

“No deal is better than a bad deal, and the president should reject this counteroffer out of hand,” he said.