WASHINGTON ― Perhaps more than any time in his historically unhinged presidency, Donald Trump is coming apart ― and the limitations of Congress to constrain the president are on full display.

Trump is facing an increasingly serious challenge, with Democrats more determined than ever to impeach him and Republicans finally showing signs of discomfort. In the latest poll, 58% of Americans now support an impeachment inquiry, with even 1 in 5 Republicans backing the move.

Support for impeachment is also still growing. Nearly every day since the public learned of a whistleblower’s complaint about a phone call between Trump and Ukrainian President Volodymyr Zelensky, there has been another bombshell discovery that leaves GOP lawmakers struggling to defend Trump’s actions. Trump himself seems to have settled on a strategy where he and his administration completely refuse to cooperate with Congress.

On Wednesday, he ordered the U.S. ambassador to the European Union, Gordon Sondland, not to testify before the House Intelligence Committee’s investigation into the July phone call with Ukraine. And later in the day, Trump’s White House counsel sent a letter to House leaders telling them that the president wouldn’t comply with their “unauthorized impeachment inquiry.”

While Trump throws a legal temper tantrum over the investigation into Ukraine, he has also made one of the rashest foreign policy decisions of his presidency: pulling U.S. troops out of northern Syria, opening the way for the Turkish military to attack the United States’ Kurdish allies.