The House of Representatives is launching a formal impeachment inquiry against President Donald Trump, who becomes just the fourth U.S. president to face impeachment. On Tuesday, House Speaker Nancy Pelosi accused Trump of betraying his oath of office, the country’s national security and the integrity of the country’s election system.

Speaker Nancy Pelosi: “I’m announcing the House of Representatives moving forward with an official impeachment inquiry. I’m directing our six committees to proceed with their investigations under that umbrella of impeachment inquiry. The president must be held accountable. No one is above the law.”

For months, Speaker Pelosi had resisted calls by progressive Democrats to back impeachment, but that changed after President Trump publicly admitted he urged the president of Ukraine to open a probe into the dealings of his potential 2020 rival Joe Biden and his son Hunter, who served on the board of one of Ukraine’s largest natural gas companies. Trump has also admitted to withholding $391 million in aid to Ukraine. On Tuesday, President Trump dismissed the impeachment inquiry.

President Donald Trump: “Look, it’s just a continuation of the witch hunt. It’s the worst witch hunt in political history.”

The Ukraine scandal came to light after a whistleblower in the intelligence community wrote an internal complaint about Trump’s actions. On Tuesday, the Republican-controlled Senate unanimously passed a nonbinding resolution calling on the Trump administration to release the whistleblower’s complaint. Meanwhile, the actions of Trump’s personal attorney Rudy Giuliani in Ukraine are facing new scrutiny. The Washington Post reports he pursued a shadow agenda on Ukraine pushing aside key foreign policy officials. We’ll have more on the impeachment inquiry after headlines.