AS the chief ethics lawyer in the White House Counsel Office, I helped President George W. Bush with the nomination and confirmation of Chief Justice John G. Roberts Jr. and Justice Samuel A. Alito Jr. to the Supreme Court.

We were fortunate to have a Republican-controlled Senate at the time. Some Democratic senators talked of filibustering these nominations, but the president knew that the senators wouldn’t filibuster, just as they would not refuse to attend the confirmation hearing. Senators can vote against a Supreme Court nominee after holding a hearing, but refusing to vote on a nominee at all is unthinkable. Voters expect their senators to do their jobs.

Things would have been somewhat different if President Bush had needed to fill a Supreme Court vacancy during his last two years in office, when Democrats controlled the Senate. The Senate Judiciary Committee would have carried out its constitutional duty to consider a nominee, but Democrats probably would have voted down anyone they thought was too conservative. President Bush would have recognized this, and most likely would have sent the Senate a very different type of nominee, someone Republicans and Democrats could agree on. Someone like Judge Merrick Garland on the Court of Appeals for the District of Columbia Circuit.

We all remember what happened to President Ronald Reagan’s nominee Judge Robert Bork. He got a hearing, a (usually) polite reception and meetings with senators, and then a “no” vote on the Senate floor. In years when the government is divided, a nominee who is too conservative or too liberal is likely to be rejected.