House Republicans who opposed the defunding of Obamacare are beginning to speak out and are threatening to withdraw their support for the strategy if the government shutdown persists.

The growing group of lawmakers was publicly silent until now, voicing concerns privately only to their GOP colleagues while publicly rallying around the proposal, in part, to ensure the GOP caucus maintained a united front. With the government now closed and Democrats refusing to negotiate any changes to Obamacare, these Republicans are saying flatly that they've had it.

The tipping point for these Republicans came Monday, when Senate Democrats rejected for the third time a House Republican proposal to keep the government open while slowing down Obamacare. Rep. Devin Nunes, R-Calif., labeled as "lemmings" fellow Republicans who continued to use the threat of a government shutdown to stall Obamacare even after it was clear it wouldn't work.

“Doing what they’re doing is not being a conservative,” Nunes told the Washington Examiner. “Conservatives know how to count, and there has to be some game plan where you’re going to get to the end or you’re going to score. ... I just can't tell my constituents that I’m shutting down the government for nothing."

There are 233 Republicans in the House, and most of them never approved of using the threat of a government shutdown to slow Obamacare, a strategy spearheaded by Sens. Ted Cruz, R-Texas, and Mike Lee, R-Utah, and adopted by a few dozen House Republicans. It was plainly obvious that the GOP did not have the 60 votes needed to advance the bill in the Democratic Senate and Republicans didn't have enough votes in either chamber to override President Obama's certain veto.

Polls have shown since July that voters don't like Obamacare, but those same voters also didn't want the government to be shut down in a fight over the new health care law. But skeptics, including House Republican leaders, signed on to the strategy a few weeks ago because they thought it was the only way they could muster the 217 GOP votes needed to pass a temporary government funding bill.

Many of those Republicans who went along, however, are losing patience. Some are now pressuring House Speaker John Boehner, R-Ohio, to put up a "clean" budget bill that would fund the government but leave Obamacare alone. It's the kind of bill Senate Democrats have been demanding and it could be the one path to a reopening of the government. Many favor extracting concessions in the budget fight, but they have to be achievable concessions.

“I supported this whole strategy because we had members — House and Senate — who believed … that if we put on the CR defunding Obamacare that they could break that down. It didn’t work,” Rep. Mario Diaz Balart, R-Fla., said. “If one strategy isn’t working, you should probably find another strategy to try to get your point across.”

Senate Democrats and Obama insist they will not negotiate changes to the Affordable Care Act and the Senate proved it by repeatedly rejecting all Republican proposals that included the health care law.

Monday night, just hours before the midnight shutdown, Senate Democrats even took a risky vote to protect the unpopular employer health care contribution for members of Congress and their staffs. Members and staff must begin accessing their health insurance through the Obamacare exchanges in January, but are being allowed to keep their federal employer health insurance perk, which has infuriated voters.

If Democrats wouldn't even agree to negotiate such an unpopular feature of Obamacare, some House Republicans said it was time to adjust their strategy.

Underlying all of this is simmering resentment that a majority of Republicans have felt whipsawed by Cruz and Lee and a bloc of young lawmakers who cared less about the endgame than waging the fight.

“I’m really proud of the fight that we have waged here to advance our agenda. It needed to be done; the Affordable Care Act is not good for America,” Rep Scott Rigell, R-Va., said. “But that said, the question before us is, does a continued shutdown advance our agenda. And, my conclusion is that it doesn’t.”