With lawmakers set to Wednesday to authorize President Joe Biden’s impeachment inquiry, one GOP lawmaker could tank House Republicans’ case against the president.

Rep. Ken Buck (R-CO) told CNN on Tuesday that he is struggling with how to vote when lawmakers vote on the impeachment inquiry.

“I’m struggling right now, I have to tell you,” Buck told CNN anchor Erin Burnett, who asked how he plans to vote. “On the one hand, I have come out strongly and said there is no direct evidence linking President Biden to the activities of Hunter Biden. And I have, at the same time, the White House who recently sent a letter after these committees issued subpoenas to the White House. The White House sent a letter back and said, you haven’t held an impeachment inquiry vote yet, and we’re not going to give you any records until you pass an impeachment inquiry. I think that is an absolutely wrong position and it’s a delay tactic which would necessitate Congress going to the courts and having the courts enforce the subpoenas. So, I wish the White House hadn’t done that. I don’t think there is direct evidence. I’m struggling, and I want to read the resolution before making a final decision on whether to vote for it or not.”

House Republicans hold a narrow majority over Democrats. With all House Democrats expected to vote against authorizing the impeachment inquiry, Buck’s vote could prove vital on Wednesday. The lawmaker has been critical of House Republicans and has maintained that there is no evidence of wrongdoing against the president.

“Without doubt, Hunter Biden’s shady business deals undermined America’s image and our anti-corruption goals, and his conduct was thoroughly reprehensible. What’s missing, despite years of investigation, is the smoking gun that connects Joe Biden to his ne’er-do-well son’s corruption,” Buck wrote for The Washington Post.

Despite Buck’s uncertainty, House Speaker Rep. Mike Johnson said he believes House Republicans have the vote to authorize the impeachment inquiry.

“Tomorrow we’ll be voting on the inquiry,” Johnson said. “Why are we doing that? Because it’s the next necessary step. The White House has stonewalled this investigation. It’s gone methodically, carefully, as the Constitution requires of us. It’s a very serious matter. But right now, they are not turning over documents and they’re not turning over key witnesses and we will have to defend our subpoenas in court. So, to do that, you need an impeachment inquiry vote from the full House. We will have that tomorrow, I believe it will pass and we will be in the best position to continue to do our constitutional responsibility.”