Noah R. Feldman, a witness called by Democrats in the impeachment inquiry into President Trump, cautioned Thursday against the House of Representatives not sending its findings to the Senate.

Reacting to the House not having formally notified the Senate of the two articles of impeachment passed this week, the constitutional scholar said that could be a “serious problem” if the articles remain in limbo.

“Impeachment as contemplated by the Constitution does not consist merely of the vote by the House, but of the process of sending the articles to the Senate for trial,” Mr. Feldman wrote in an editorial. “Both parts are necessary to make an impeachment under the Constitution: The House must actually send the articles and send managers to the Senate to prosecute the impeachment. And the Senate must actually hold a trial.”

“If the House does not communicate its impeachment to the Senate, it hasn’t actually impeached the president. If the articles are not transmitted, Trump could legitimately say that he wasn’t truly impeached at all,” Mr. Feldman wrote for Bloomberg.

Should the House indefinitely delay sending its findings to the Senate, “then Trump could say with strong justification that he was never actually impeached,” Mr. Feldmanadded.

“And that’s probably not the message Congressional Democrats are hoping to send,” he concluded.

Mr. Feldman, a law professor at Harvard University, was chosen by Democrats to testify during the first public impeachment hearing held this month by the House Judiciary Committee.

Appearing before Congress on Dec. 4, Mr. Feldman said he believed that Mr. Trump “committed impeachable high crimes and misdemeanors by corruptly abusing the office of the presidency.”

The Democratic-controlled House subsequently voted Wednesday to pass articles of impeachment against Mr. Trump for both abuse of power and obstruction of Congress. Speaker Nancy Pelosi of California has not yet committed to sending those articles to the Senate, however, where Mr. Trump is likely to be acquitted at trial by its Republican majority.