Rep. Tulsi Gabbard on Friday said she supports the House’s newly formal inquiry into whether to impeach President Trump, after she had repeatedly said impeachment would be too divisive for the country.

She said after reviewing the latest evidence and reports on Mr. Trump’s interactions with Ukrainian President Volodymyr Zelensky, it would set a “very dangerous precedent” if the House didn’t proceed.

“It is unfortunate, but necessary, that I speak in support of the inquiry into the president’s alleged abuse of power in relation to his interactions with Ukraine’s leaders,” said the Hawaii Democrat and 2020 presidential candidate.

She called for a “swift, thorough, and narrowly focused” inquiry.

“If we allow the president to abuse his or her power, then our society will rot from top to bottom,” she said. “We will turn into a banana republic, where people in positions of power — from the president all the way down to the traffic cop — will feel it’s OK to abuse their power with no consequences.”

Ms. Gabbard had been one of the more prominent Democratic holdouts on impeachment, and her opposition stood out in a Democratic presidential field that has generally welcomed and encouraged the prospect of impeachment.

House Speaker Nancy Pelosi announced earlier this week that the House would formally open an impeachment investigation.

Many Democrats who were on the fence have cited the recently disclosed whistleblower complaint alleging that Mr. Trump pressured Mr. Zelensky to investigate Democratic presidential candidate Joseph R. Biden as the final tipping point.