WASHINGTON—President Donald Trump picked a nominee for the Supreme Court hours before a scheduled announcement, and multiple people close to the White House expected the rollout of Brett Kavanaugh, a fixture of the District of Columbia Circuit Court.

On Monday, Mr. Trump had settled on two finalists and was leaning toward Judge Kavanaugh based on what he saw as an impressive academic pedigree and judicial credentials, one person close to the White House said.

Mr. Trump had wavered for days about the choice, taking the decision to the final hours before the scheduled prime-time announcement Monday night. Judges Kavanaugh and Thomas Hardiman emerged as the finalists along with two other judges, Raymond Kethledge and Amy Coney Barrett, but Sen. Orrin Hatch (R., Utah) suggested late Monday that Mr. Trump had ruled out Judge Barrett.

Ahead of the announcement, Judge Hardiman’s supporters began preparing Monday for a rollout in the event the president selected him to fill the vacancy created by Justice Anthony Kennedy’s retirement. But as the hour of the announcement drew closer, multiple people said they were anticipating the president was ready to announce he had chosen Judge Kavanaugh instead.

Mr. Trump had reached the decision as of noontime in advance of a scheduled 9 p.m. ET announcement, a White House official said. About an hour later, the White House said that former Republican Sen. Jon Kyl of Arizona, a longtime member of the Senate Judiciary Committee, would guide Mr. Trump’s pick through the confirmation process in the role of “sherpa.”