President Donald Trump faces an impeachment inquiry initiated officially in a vote of the House of Representatives on Oct. 31.

Mack Shelley, Iowa State professor and chair of the political science department, said House Speaker Nancy Pelosi was “strategic” in her announcement.

“Pressure had been growing within the Democratic caucus in favor of impeachment, and the whistleblower had revealed information that made Trump seem more vulnerable,” Shelley said.

Prior to the vote, Pelosi announced the opening of the inquiry and closed-door hearings on Sept. 24. The FiveThirtyEight average of polls on impeachment finds that since five days after Pelosi announced the opening of the inquiry, more Americans do not support Trump’s impeachment. As of Sunday, 48.8 percent support his impeachment compared to 43.5 percent who do not. 

Trump faces the impeachment inquiry following allegations from an anonymous whistleblower that Trump withheld military assistance to Ukraine as the nation faces occupation by Russian-backed militias in its east and occupation of its southern territory of Crimea by Russia itself.

Trump allegedly sought to pressure the Ukrainian President Volodymyr Zelensky to investigate Democratic presidential-frontrunner former Vice President Joe Biden and his family in exchange for the release of the military aid.

During public testimony before the House Intelligence Committee on Nov. 20, Gordon Sondland, the United States ambassador to the European Union, said there were several conversations between himself and Trump regarding Ukraine opening investigations into Biden’s family and a conversation regarding the possibility Ukraine meddled in the 2016 presidential election, a theory for which no evidence has surfaced.

The theory Ukraine did so was rejected in public testimony on Nov. 21 by Fiona Hill, a former National Security Council adviser to Trump.

“This is a fictional narrative that has been perpetrated and propagated by the Russian security services themselves,” Hill said. “The unfortunate truth is that Russia was the foreign power that systematically attacked our democratic institutions in 2016.”

The impeachment proceedings have slowed to a halt for the Thanksgiving holiday, though more public hearings are scheduled to begin Wednesday in the House Judiciary Committee.

“[Chairman of the House Intelligence Committee] Adam Schiff has indicated that further hearings in the [intelligence committee] are possible, but that will depend largely on whether court rulings uphold congressional subpoenas,” Shelley said.