(CNN) — House Speaker Nancy Pelosi on Tuesday announced a formal impeachment inquiry into President Donald Trump, a dramatic move that signals a change in Pelosi’s political calculation and comes as the President faces outrage over reports that he pressured a foreign leader in an effort to target a political rival. The announcement marks the most direct step taken by the House Democratic leader to embrace impeachment proceedings and is a significant escalation in the fight between House Democrats and the President. “The actions of the Trump presidency revealed the dishonorable fact of the President’s betrayal of his oath of office, betrayal of our national security and betrayal of the integrity of our elections,” Pelosi said in a news conference. “Therefore, today, I am announcing the House of Representatives moving forward with an official impeachment inquiry. “The House speaker, who has long pushed to keep her caucus away from the politically divisive issue, is signaling that she’s responding to the seismic shift among Democratic members, following Trump’s admission of discussing Vice President Joe Biden and his son in his phone call with the Ukrainian President. Dozens of House Democrats — many from moderate or Trump-won districts — have announced their support for an impeachment inquiry over the past 48 hours.