No one will shape the fate of Donald Trump in the coming days more than Senate Majority Leader Mitch McConnell (R-Ky.), who has left open the possibility of voting to convict the outgoing president over the deadly attack on the U.S. Capitol.

As the House was voting Wednesday to impeach Trump for a second time, McConnell said in a note to his fellow GOP senators that he is undecided on whether to convict the president. He pledged in the letter to listen to the legal arguments when they are presented to the Senate, which is expected to begin immediately after Joe Biden is inaugurated on Jan. 20.

The Kentucky Republican is notoriously pithy, so him saying he isnt ruling out voting to convict Trump is notable, and is likely intended to serve as a message against further incitement and chaos from White House.

If McConnell were to actually vote against Trump, the math would shift dramatically in favor of conviction: More GOP senators would likely join Trump critics who are already expected to vote to convict, including Sens. Susan Collins of Maine, Lisa Murkowski of Alaska, Mitt Romney of Utah, Ben Sasse of Nebraska, and Pat Toomey of Pennsylvania.

No one knows what the majority leader will do. The vote presents McConnell and other Republicans with one last chance to separate themselves from Trumps toxicity, and possibly even bar him from running for federal office ever again. The trial will also help write one of the final chapters of McConnells legacy. In exchange for tacitly supporting Trump and all his chaos, McConnell transformed the federal judiciary with hundreds of conservative judges and tipped the scales in favor of the GOP for decades.