Sen. Ron Johnson (WI) says the tax plan benefits corporations more than any other kind of business, and for that reason he is opposed to the bill, the Wall Street Journal reports. "If they can pass it without me, let them. I'm not going to vote for this tax package," Johnson told WSJ.

Why it matters: Unless they get Democrats on board, Republicans can only afford to lose two GOP votes. This is one.

Correction: This post has been updated to correct an editor's error. Republicans can afford to lose two votes, not three.