Yet the GOP leadership has a narrow window to push through its tax bill in the Senate before lawmakers become consumed with spending fights that could trigger a shutdown, not to mention a special election in Alabama that could flip a reliable Republican vote to a not-so-reliable one — or even a Democrat…

An influential and independent-minded bloc of deficit hawks, including Sens. Bob Corker of Tennessee and Jeff Flake of Arizona, have aired deep concerns about the tax bill’s red ink, even accounting for any economic growth that a tax overhaul might generate. Sens. Susan Collins of Maine and Jerry Moran of Kansas have voiced concerns about including in the tax proposal language that would repeal Obamacare’s individual mandate.

Sen. Ron Johnson (R-Wis.), so far the only declared “no” on the tax legislation, has argued that the overhaul unfairly disadvantages small businesses — although to fix the bill to his liking, the changes would likely cost hundreds of billions of dollars. Sen. Steve Daines (R-Mont.) has expressed similar concerns on so-called pass-throughs, according to Republicans.