Democrats in the U.S. House of Representatives are moving to formally start impeachment proceedings against President Donald Trump, in the wake of the president’s confirmation that he withheld aid from Ukraine while at the same time urging the country’s leader to investigate the son of former Vice President Joe Biden, who is running to be Trump’s Democratic opponent in the 2020 presidential election.

Those developments, reportedly the subject of a whistleblower complaint made to the intelligence community’s inspector general, have pushed House Speaker Nancy Pelosi, D-California, to publicly back the effort after she repeatedly declined to do so for several months.