Sen. Ron Johnson (R., Wis.) said he opposes the Senate Republican tax package, saying it unfairly benefits corporations more than other types of businesses.

"If they can pass it without me, let them," Mr. Johnson said in an interview. "I'm not going to vote for this tax package." With 52 seats in the Senate, Republicans can lose no more than two votes unless they can somehow find a way to win votes from Democrats.

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