Sen. Rand Paul could force a vote on the Senate floor that would bring Hunter Biden or other White House-favored impeachment witnesses to an impeachment trial.

Paul said on Thursday he’s considering forcing votes on motions in President Donald Trump’s impeachment trial allowing Trump to bring his own witnesses. The Kentucky senator and close Trump ally has urged Congress to call Hunter Biden as a witness for his work at a Ukrainian energy company.

The House’s impeachment inquiry is investigating whether the president abused his power when he pressured Ukraine to investigate Joe Biden and his son Hunter in exchange for military aid.