WASHINGTON — President Donald Trump has narrowed his list of contenders to replace retiring Supreme Court Justice Anthony Kennedy to three serious candidates, a source familiar with the selection process told NBC News on Thursday.

Those candidates are appeals court judges Brett Kavanaugh, Raymond Kethledge and Amy Coney Barrett, the source, who was not authorized to speak publicly, said.

Kavanaugh, 53, and Kethledge, 51, are both former law clerks to Kennedy, as was Neil Gorsuch, Trump's first Supreme Court nominee, who succeeded Antonin Scalia. Kavanaugh, also a veteran of George W. Bush’s White House, currently serves on the U.S. Court of Appeals for the District of Columbia.

Kethledge currently serves on the 6th Circuit Court of Appeals. Barrett, 46, is a former law clerk to Scalia and was appointed by Trump last year to serve on the 7th Circuit Court of Appeals. Barrett, if selected and confirmed, would be the youngest justice on the high court.

Kennedy, a reliable swing vote on the nine-member court, announced his retirement in late June. Over the past week, the president interviewed several candidates and promised that his pick would be a "home run."

In recent days, Vice President Mike Pence has also met with a few of the Supreme Court contenders, a source familiar with the process told NBC News. However, the source did not identify which candidates Pence met with.

With Kennedy's departure from the court, Democrats and liberal-leaning groups are gearing up for a major confirmation fight, arguing that a potential pick should be selected and confirmed after the midterm elections in November.

Trump has said he plans to announce his choice on Monday.

CORRECTION (July 5, 3:20 p.m.): An earlier version of this article misstated where Judge Raymond Kethledge, one of the top candidates for a Supreme Court appointment, attended law school. It was the University of Michigan Law School, not Yale Law School.