On September 24, 2019 Nancy Pelosi announced that a formal impeachment inquiry was launched to investigate President of the U.S. Donald Trump. The inquiry came after formal complaint filed by an unidentified whistleblower about a phone call between Trump and the President of Ukraine Volodymyr Zelensky. In this phone call, Trump asked Zelensky to investigate Trump’s political rival, former Vice President Joe Biden, after making remarks on Ukrainian dependence on U.S. military aid. This conversation came after the Trump Administration withheld aid from Ukraine, the Washington Post reported.

Democrats in Congress also have text messages between top U.S. envoys in Ukraine. In these messages, it was made clear to Zelensky that a White House visit to meet Trump was dependent on him making a public statement vowing to investigate Hunter Biden’s company, according to The Guardian.

Democrats are calling the phone call and the messages evidence of a demand for quid pro quo by Trump which is treasoous under the Constitution. Since the initial complaint, a second intelligence official with more direct knowledge regardingTrump’s dealings with Ukraine is considering filing a whistleblower complaint, New York Times reported. The lawyer representing the first whistleblower Mark Zaid confirmed that he is now representing this second person according to CNN. He did not confirm if his second client was the same person the New York Times reported on. Potentially, there could be three whistleblowers.

House Intelligence Committee Chair Adam Schiff told The GuardianTrump’s requests to China and Ukraine were, “an illustration that if this President has learned anything from the two years of the Mueller Investigation is that he feels he can do anything with impunity.” Trump has since then said that there was no quid pro quo or any exchange on the phone call.

The only two presidents ever impeached in U.S. history were Andrew Johnson in 1868 on charges of violating the Tenure of Office Act by removing Secretary of War Edwin Stanton from office, and Bill Clinton in 1998 on charges of perjury and obstruction of justice in the settlement of a sexual harassment lawsuit brought by Paula Jones. However, both of them were acquitted during trial and stayed in office to serve the rest of their term.