Republican Sen. Ron Johnson announced he is opposed to the tax bill Wednesday, making him the first member of the GOP to formally come out against the party’s plan.

The Wisconsin told The Wall Street Journal that he is not able to vote for the bill as it’s currently written.

“If they can pass it without me, let them,” Johnson told the WSJ. “I’m not going to vote for this tax package.”

CNN has reached out to Johnson’s office for comment on his stance on the bill and has not yet gotten a response.

Johnson cited concerns with the way the Senate’s bill treats pass-through entities and argued that the bill gives larger tax breaks to corporations rather than small businesses. Johnson has previously expressed concerns about how small businesses are treated in the Senate bill, but he had not formally announced his opposition until Wednesday.

Johnson’s opposition means that Republican leaders are once again facing a very narrow path to passage. Senate Majority Leader Mitch McConnell can only lose two members of his conference and pass the bill along party lines. With Johnson out, all eyes turn to other members who may be concerned about the announcement Tuesday that the Senate Republicans would include a repeal of the individual mandate in their tax bill.

Repealing the individual mandate failed earlier this year after Sens. John McCain of Arizona, Susan Collins of Maine and Lisa Murkowski of Alaska voted against a bill to repeal and replace the Affordable Care Act. None of those members have come out officially against the tax bill, however.