Jonathan Turley, the constitutional scholar at George Washington University whom House Republicans had chosen to testify in the House Judiciary Committee’s impeachment hearings, smacked down the White House’s legal argument in the Senate trial on Tuesday.

In an op-ed published in Washington Post, Turley took aim at White House Counsel Pat Cipollone and Trump lawyer Jay Sekulow’s claim that the President cannot be impeached because he did not commit a crime when he withheld military aid to Ukraine while asking Ukrainian President Volodymyr Zelensky to investigate Joe Biden.

“It is a view that is at odds with history and the purpose of the Constitution,” the legal expert wrote of Cipollone and Sekulow’s defense.

He warned that adopting their interpretation of impeachable offenses “would create lasting harm for the constitutional system” because it is “far too narrow.”

Turley compared the White House’s argument to Democrats’ defense of President Bill Clinton in 1999, which “created a dangerous precedent” for “criminal, non-impeachable conduct.”

“The developing defense by the White House is also a mistake. It would again ‘expand the space for executive conduct’ by reducing the definition of impeachable conduct to the criminal code,” the lawyer wrote. “It is an argument that is as politically unwise as it is constitutionally shortsighted.”

House Republicans had appointed Turley as their witness in the House Judiciary Committee’s impeachment hearing in December, during which he argued that the Democrats’ legal case for Trump’s impeachment was “not just woefully inadequate, but in some respects, dangerous, as the basis for the impeachment of an American president.”

“I am concerned about lowering impeachment standards to fit a paucity of evidence and an abundance of anger,” he said at the time. “If the House proceeds solely on the Ukrainian allegations, this impeachment would stand out among modern impeachments as the shortest proceeding, with the thinnest evidentiary record, and the narrowest grounds ever used to impeach a president.”