The routine Capitol Hill negotiations in which Democrats and Republicans try to reach a short-term deal to fund the federal government after September is expected to be especially complex this year as both sides hint they will allow a government shutdown over such key issues as sequestration and ObamaCare.
Republicans essentially have tried to dismantle the president's signature health-care legislation since he signed it into law in 2010, including 38 related votes in the GOP-led House. And Republicans say defunding it next year is their last, best chance.
"If you pay for a budget that pays for ObamaCare ... you have voted for ObamaCare," said Sen. Marco Rubio, R-Fla. "Some will say, `That is crazy. You are going to shut down the government over ObamaCare.' No. What is crazy is moving forward with this."
The negotiation is to agree on a short-term measure -- known as a “continuing resolution” -- to fund the government for a few weeks or months until a larger deal can be reached on appropriations bills that give federal agencies their full fiscal 2014 operating budgets, which begin Oct. 1.
To be sure, Washington lawmakers would like to avoid the political disaster of 1995-1996 when failed negotiations between congressional Republicans and Democratic President Bill Clinton resulted in a shutdowns for 28 days.
However, Republicans are being pushed especially hard recently over ObamaCare by the Tea Party movement and such conservative groups as the Heritage Foundation and the Club for Growth, which has a history of backing conservative challengers to GOP incumbents in party primaries.
The anti-tax group Club for Growth is asking Senate Minority Leader Mitch McConnell to sign a letter circulated by Utah Republican Sen. Mike Lee promising not to fund ObamaCare through any budget or continuing resolution in September.
Lee has signatures from 11 Senate Republican colleagues since Thursday when he began circulating the letter, which is addressed to Majority Leader Harry Reid.
Meanwhile, some Democrats also are taking a hard-line position this time -- vowing a shutdown unless Republicans agree to replace the austere federal spending cuts known as sequestration with less drastic ones.
Sequestration, which started in March after Washington failed to agree on a more measured approach to spending reductions, has since cut $55 billion -- about 5 percent -- from the day-to-day operating budgets of federal agencies.
"There are lots of progressives who care about domestic discretionary spending who think that the Republicans are winning because with the sequester we have a gradual downsizing of the government going on that nobody's doing anything about,” said Democratic strategist Steve Elmendorf. “If we just let it keep happening without having a confrontation about it we're losing. And Sept. 30 becomes a place to have a confrontation about it."
Democrats insist, at a minimum, that spending should continue at rates consistent with the current $988 billion cap on appropriations for the 2013 budget year ending Sept. 30. But current law sets a lower cap of $967 billion for 2014 as required by sequestration.
Both parties have acknowledged a shutdown would just re-enforce voter perception that Washington is dysfunctional, ahead of lawmakers in both Capitol Hill chambers seeking re-election in 2014.
Though the president has made several veto threats over the past several weeks, it remains unclear whether he and his advisers would agree to a vetoing a continuing resolution with sequester-level funding.
"The American people will not look kindly upon action taken here in Washington to shut down the government," White House Press Secretary Jay Carney said this week.
At the same time, some Republicans also appear nervous about forcing a shutdown.
"I think it's the dumbest idea I've ever heard," said Sen. Richard Burr, R-N.C. "Some of these guys need to understand that if you shut down the federal government, you better have a specific reason to do it that's achievable. ... At some point, you're going to open the federal government back up, and Barack Obama's going to be president, and he won't have signed a dissolution of the Affordable Care Act."
Rep. Tom Cole, R-Okla., whose views usually reflect those of House Speaker John Boehner said: "Shutting down the government, I think, that's almost never a good tactic. … It wasn't good for us in 1995. It's not going to be good for us in 2013."
The Associated Press contributed to this report.