Congress formally opened a new, public phase of its corruption investigation into Donald Trump on Thursday as US lawmakers voted for the first time to advance the impeachment process targeting the US president.
"Today the House takes the next step forward as we establish the procedures for open hearings... so that the public can see the facts for themselves," House Speaker Nancy Pelosi said.
"What is at stake in all of this is nothing less than our democracy."
The embattled president retweeted a rallying cry from Fox News host Laura Ingraham that called on Republicans to "stand together and defend the leader of their party against these smears."
"If we don't hold this president accountable, we could be ceding our ability to hold any president accountable."