Stanford Law School's Pamela Karlan is expected to testify before the U.S. House of Representatives Judiciary Committee today that Donald Trump must be held accountable for demanding foreign interference into the 2020 presidential elections to smear a political opponent.

Karlan is among four law professors who are set to testify before the House Judiciary Committee this morning as it starts its portion of the impeachment inquiry, which is investigating whether Donald Trump withheld aid to Ukraine in exchange for a public pledge that the nation's newly elected government open an investigation into Joe Biden and his son, Hunter Biden.

"Based on the evidentiary record, what has happened in the case before you is something that I do not think we have ever seen before: a president who has doubled down on violating his oath to 'faithfully execute' the laws and to 'protect and defend the Constitution,'" Karlan is expected to say, according to a copy of her prepared remarks. "The evidence reveals a president who used the powers of his office to demand that a foreign government participate in undermining a competing candidate for the presidency."