WASHINGTON Whether or not Republicans ever agree to a budget deal with President Barack Obama, one thing seems certain: Now that he has officially put Social Security and Medicare benefits on the negotiating table, opponents on his party's left will make that an issue for Democrats in the midterm elections next year and perhaps in the 2016 presidential contest.
In the midterm races already taking shape, Democrats who back Obama's budget proposals to trim future benefits as part of a long-term deficit-reduction compromise could be attacked from the left and the right.
Liberal groups and some union leaders are threatening to recruit candidates to challenge these Democrats in their primaries. At the same time, the head of the House Republicans' campaign committee gleefully signaled last week that he would use Obama's "shocking attack on seniors" against Democrats in general-election races though Republican congressional leaders demanded the concessions from Obama.
And while party leaders rebuked the campaign committee chief, Rep. Greg Walden of Oregon, individual Republican candidates and super PACs would be free to wage their own attacks.
For now, at least, the political warnings to Democrats are coming mostly from the left of their own party.
"You cannot be a good Democrat and cut Social Security," said Arshad Hasan, executive director of Democracy for America, a liberal grass-roots group, which staged a small protest outside the White House last week even before Obama released his annual budget on Wednesday.
"People would be looking to punish them," said Robert Borosage, a co-founder of the Campaign for America's Future, another liberal group, "and they would be looking for primary challengers."
Even if Democratic incumbents do not draw a primary challenger, liberal activists say, they might face a shortage of volunteers motivated enough to do the hard work of campaigning just as Democrats did in the 2010 midterms, which resulted in big Republican gains.
Looking further ahead, to 2016, some on the left have already begun talking about encouraging a liberal Democrat the freshman Sen. Elizabeth Warren of Massachusetts is the name most mentioned to take up the "don't touch Social Security or Medicare" banner as part of a liberal bid for the party's nomination to succeed Obama, even against Hillary Rodham Clinton, the former secretary of state, or Vice President Joe Biden should either run.
Such talk was stoked when Warren, within hours of the release of the president's budget on Wednesday, sent supporters an email sounding an alarm: "Our Social Security system is critical to protecting middle-class families, and we cannot allow it to be dismantled inch by inch." She was not available for an interview, aides said Friday.
"If the major candidates running for the Democratic nomination hedge on important issues like Social Security, they will leave open a tremendous amount of space for an insurgent," said Adam Green, a co-founder of the Progressive Change Campaign Committee, a group often critical of Obama.
But, Green acknowledged, "I wouldn't say anybody's laying the groundwork yet."
At a minimum, Borosage said, all Democratic candidates in 2014 or 2016 "will be forced to take a stand."
That prospect could complicate the campaign strategies of establishment favorites.
Biden is inevitably tied to Obama's policies. And Clinton, as a senator, was a fiscal moderate who extolled her husband's budget-balancing record of compromise.
President Bill Clinton negotiated Medicare savings with congressional Republicans, and their 1997 deal nearly included the same proposal trimming Social Security cost-of-living increases that Obama has put in his budget to entice Republicans to compromise in turn.
As his second term began, Obama used his annual budget proposal to make his most public overture toward compromise yet.
The budget, incorporating the final December offer to House Speaker John Boehner, also proposed other cuts in spending for domestic programs and the military and $400 billion in savings over 10 years from Medicare. Those savings would come mostly from reducing payments to hospitals and pharmaceutical manufacturers, but also from trimming benefits and raising out-of-pocket costs for higher-income beneficiaries.
Liberals found much to praise, like Obama's proposed new spending for road construction, nationwide pre-kindergarten education and advanced manufacturing research; a higher federal minimum wage; and reduced tax breaks for the wealthy.
But they were stunned that he proposed the new cost-of-living formula. With that as the kindling, their opposition movement intensified.
More than two years away from Democrats' presidential-nominating contest, however, it is hard to see who could or would become the left's standard-bearer.
Besides Warren, other party leaders mentioned include Gov. Andrew M. Cuomo of New York, Gov. Martin O'Malley of Maryland, Sen. Kirsten Gillibrand of New York and Sen. Amy Klobuchar of Minnesota.
Certainly an unexpected candidate could emerge, as Obama did for the 2008 race. Three years before that year's nominating convention, few Democrats saw him as a likely candidate, much less one who could vanquish Hillary Clinton.
Now Clinton is again seen as the nearly invincible front-runner, should she choose to run. Many potential aspirants, including Warren, are widely considered unlikely to challenge her as Obama did in 2008.
Back then, the issue that he seized was opposition to the Iraq War. In 2004, Democrats' disgust with that war had powered Howard Dean's liberal challenge to Sen. John F. Kerry, who ultimately defeated Dean, the Vermont governor, for the nomination.
Geoff Garin, a Democratic pollster, said that while the issue of protecting Social Security and Medicare could be potent in coming congressional and presidential campaigns, it "will not be galvanizing in 2016 quite the way that voting for the Iraq War was."
"Certainly today, and presumably still at the time of the next election, President Obama has enormous credibility with Democratic voters, particularly liberal Democrats," Garin said.
That credibility extends, he added, to the president's case for making changes that bolster the finances of the social-insurance programs for future generations.
"While I have no doubt that there would be some Democratic voters who rally around a candidate who runs on a 'don't touch Social Security or Medicare' platform," Garin added, "there would not be enough to sustain a candidacy unless that candidate has a lot of other things going for him or her." WASHINGTON