Sens. Steve Daines, R-Mont., and Ron Johnson, R-Wis., will vote for the Senate Republican tax bill after securing further tax relief for pass-through businesses.

The support from the senators, two of the last GOP holdouts on the bill, nudges Republicans closer to passing the plan on Friday. Republicans are reworking their bill after a last-minute setback and hope to pass it later in the day.

"After weeks of fighting for Main Street businesses including Montana's farmers and ranchers, I've decided to support the Senate tax cut bill which provides significant tax relief for Main Street businesses," Daines said in a statement.

On Friday morning, Senate Majority Whip John Cornyn, R-Texas, called holdout Sens. Bob Corker, R-Tenn., and Jeff Flake, R-Ariz., the last two senators who need to get on board. It is unclear where that leaves holdout Sens. Susan Collins, R-Maine, and James Lankford, R-Okla., who have not yet committed to supporting the proposal.

Senate Finance Committee Chairman Orrin Hatch, R-Utah, on Friday said he believes Republicans have the votes to pass the bill. Corker told NBC News on Friday that he thinks the GOP can approve it even without his vote.