ObamaCare is at the center of a rapidly escalating fight that threatens to shut the government down this fall. [WATCH VIDEO]

Senate Republicans, including two members of the leadership, are coalescing around a proposal to block any government funding resolution that includes money for the implementation of the 2010 Affordable Care Act.

But such a move is a nonstarter for President Obama and congressional Democrats. Republicans have tried this maneuver in Obama’s first term, only to back off later to the chagrin of Tea Party leaders.

This time, GOP lawmakers are emboldened by problems plaguing the administration’s ObamaCare implementation. But that zeal could put Speaker John Boehner (R-Ohio) and Minority Leader Mitch McConnell (R-Ky.) in a tough spot. Both leaders have downplayed previous talk of shuttering the government.

In the House, 64 Republicans have signed onto a letter pressing Boehner not to bring any legislation funding ObamaCare to the floor.

Sen. Mike Lee (R-Utah), the leader of the Senate effort, predicts the vast majority of the Senate Republican Conference will back his plan, giving him enough votes to sustain a filibuster of a stopgap spending measure.

“This is the last stop before ObamaCare fully kicks in on Jan. 1 of next year for us to refuse to fund it,” Lee said Monday on “Fox and Friends.”

“If Republicans in both houses simply refuse to vote for any continuing resolution that contains further funding for further enforcement of ObamaCare, we can stop it. We can stop the individual mandate from going into effect,” he said.

“We have 64 of my colleagues on this letter and we’re asking the leadership not to bring anything to the floor that has funding for ObamaCare in it,” said Rep. Mark Meadows (R-N.C.), who is spearheading the House effort. 

Congress in recent years has regularly passed stopgap spending measures known as “continuing resolutions” to keep the federal government running beyond the end of the fiscal year. This has been necessary because lawmakers now routinely fail to finish their appropriations work by the Sept. 30 deadline.

This year, the expiration of laws appropriating government funding coincides with the start of open enrollment for healthcare exchanges set up by the Affordable Care Act.

Several influential members of the Republican conference are backing the controversial tactic, including Senate Republican Whip John Cornyn (Texas) and Sen. John Thune (S.D.), the second- and third-ranking members of the GOP leadership, respectively.

Sen. Marco Rubio (Fla.), who is widely considered a front-runner for the Republican presidential nomination in 2016, has also signed on.

Earlier this month, he spoke out in favor of holding hostage the government operation funds to freeze the rollout of the controversial healthcare law at a breakfast sponsored by Concerned Veterans for America. Those remarks were viewed as an attempt to appease the GOP base after he helped shepherd a controversial immigration bill through the Senate.

Sen. John McCain (R-Ariz.) criticized his colleagues’ strategy in a Friday interview with conservative talk show host Michael Medved.

“Some of my Republican colleagues are already saying we won’t raise the debt limit unless there’s repeal of ObamaCare. I’d love to repeal ObamaCare, but I promise you that’s not going to happen on the debt limit,” McCain told Medved, according to The Washington Post.

“So some would like to set up another one of these shutdown-the-government threats. And most Americans are really tired of those kinds of shenanigans here in Washington,” he said.

Republicans have been riding a wave of political momentum on the healthcare issue since the beginning of the month, when the Obama administration announced it would delay the requirement for employers with 50 or more workers to provide health coverage.

Emboldened House Republicans voted last week to delay the employer mandate as well as the law’s requirement that individuals buy coverage. The bills split Democrats as nearly two dozen voted for both measures.

Some Republicans, including McCain, however, fear the party may be in danger of overreaching.

“I’ve been concerned that there could be a government shutdown and I was wondering who’s going to take the blame for it, and now we know. Republicans have stepped up to the plate,” said Scott Lilly, who was serving as a Democratic aide on the House Appropriations Committee when a spending fight caused a government shutdown in 1995. 

Republicans took most of the public blame over the last shutdown, creating momentum for former President Bill Clinton’s 1996 reelection.

A senior GOP aide noted that 127 Republicans signed a similar letter to Boehner last year urging him not to advance legislation funding healthcare reform.

But conservatives argue the implementation of the law will be an economic disaster and aggressive tactics are needed to avert it.

“You want to delay implementation? Don’t fund it,” Rubio said at the July 11 breakfast. “If we have a six-month continuing resolution, we should defund the implementation of ObamaCare by those six months … I will not vote for a continuing resolution unless it defunds ObamaCare.”

An aide to Lee said Republicans won’t be blamed for a shutdown because they will offer legislation to fund all other government operations except for those necessary to establish the new healthcare law.

“This is going to be the litmus test of whether you do or do not support ObamaCare,” said Brian Phillips, Lee’s spokesman.

Lee’s proposal could become an issue in Republican primary races next year.

“Any Republican who votes to give Obama a single penny to implement ObamaCare is part of the problem and should be defeated. Any Republican who votes to fund ObamaCare should have a primary challenger,” said Matt Hoskins, executive director of the Senate Conservatives Fund, a fundraising group that supports conservative Republican challengers.