Former Vice President Joe Biden is for the first time calling for President Trump to be impeached.

“With his words and his actions, President Trump has indicted himself by obstructing justice, refusing to comply with the Congressional inquiry, he’s already convicted himself in full view of the world and the American people,” Biden told a crowd of supporters Wednesday. “Donald Trump has violated his oath of office, betrayed this nation and committed impeachable acts.”

President Trump quickly responded on Twitter, saying “I did nothing wrong” and repeating unproven allegations of corruption against Biden.

The White House, meanwhile, is refusing to cooperate with the ongoing impeachment inquiry. A letter outlining their arguments against the process accuses Democrats of violating “fairness” and “due process,” in part because the full House hasn’t voted to authorize the investigation.

The Constitution does not require a vote.

“The House does not need to hold a vote to start an impeachment inquiry, there is nothing in the Constitution that says they have to, the House can determine for itself how to conduct an impeachment inquiry,” explains Elizabeth Wydra, president of the Constitutional Accountability Center.