Usually when Majority Leader Harry Reid prevents Republicans from offering amendments, GOP senators block the underlying bill. At least, that was how Republicans handled the recently dispatched energy-efficiency bill, which went down earlier this week.
But there are signs that even if Reid blocks amendments on legislation to extend expired tax provisions, known as tax extenders, Republicans won't prevent the bill from coming to the floor.
"There's probably a lot more support among Republicans for tax extenders than there perhaps was for energy efficiency," said Sen. John Thune of South Dakota, the chamber's No. 3 Republican.
The difference, according to lawmakers, is that some of the roughly 60 provisions in the tax-extenders package benefit constituents in some way. Thune also said that members view extending current tax policy differently than they do enacting new energy legislation.
"I just think you're talking about tax policy," Thune said. "You're talking about extending tax policy. And many of them are things that our members are supportive of."
Of course, there are some provisions in the bill that Republicans oppose. "So it's hard to say at this point how that vote might go," Thune said. "But I wouldn't necessarily guarantee that it's gonna turn out the same way that the energy [efficiency] cloture vote did."
GOP Sen. Tim Scott of South Carolina said that whether he votes for the underlying measure depends on whether Reid allows amendments, but that he expects there is enough support in the conference for the measure to clear procedural hurdles.
"What they've said is there's so much stuff in there that is necessary to move our economy forward that perhaps this isn't the time to make a philosophical or process stand," Scott said.
At the same time, conservative groups are making the case that this is precisely the time to take a stand against extending the tax provisions. Heritage Action, the Club for Growth, and FreedomWorks have each come out against the Expire Act, as the legislation is known.
The problem, some conservatives argue, is that the tax extenders benefit special interests, rather than the taxpaying public overall.
"That approach to legislating is how our tax code became so convoluted in the first place," Heritage Action spokesman Dan Holler said in a statement. "Comprehensive, pro-growth tax reform will remain elusive until it becomes clear to special interests their favored provisions are no longer sacrosanct."
But Republicans who sound supportive of letting the legislation move forward aren't fazed by the conservative headwinds.
"Different organizations are going to come to different conclusions," Thune said. "You're gonna have an awful lot of support from the business community."
Indeed, there are conservative groups backing the legislation. Americans for Tax Reform, the group headed by Grover Norquist, and the U.S. Chamber of Commerce are among them. They want to see the extenders folded into a broader overhaul of the tax code, but argue they help businesses and families in the meantime.
"For now, though, the mandate for the Senate is clear: Do no harm," Americans for Tax Reform said in a statement.
Even if the measure gets through the Senate, it will stall in the House, which is considering the provisions discretely, rather than in a single package.
Action on the bill isn't expected to wrap up until next week, aides said, and in the meantime Republicans have not ceased calling for amendments, with leaders saying they expect a repeal of the medical-device tax will be offered.
Thune has introduced eight amendments, including several Obamacare measures and one that would make the state and local sales-tax deduction permanent. In addition, Republican Sens. Jeff Flake of Arizona and Lamar Alexander of Tennessee said they plan to jointly offer an amendment to repeal the wind-energy tax credit.
Even so, Republicans are already expecting Reid to rebuff their efforts to amend the legislation.
Sen. Jeff Sessions of Alabama said he hasn't decided whether he'll vote against procedural measures if Republicans are not allowed amendments, but he pointed out that doing so has been the norm for him.
"This is so contrary to the heritage of the Senate, no matter what the issue is before us," Sessions said. "We've got to end this."