US President Obama on Wednesday will nominate Merrick B. Garland as the nation’s 113th justice, according to White House officials

US President Obama on Wednesday will nominate Merrick B. Garland as the nation’s 113th justice, according to White House officials, choosing a centrist appeals court judge widely respected even by Republicans in hopes his choice will be considered by the Senate.

In choosing Judge Garland, a well-known moderate who has drawn bipartisan support over decades, Mr. Obama was essentially daring Republicans to press their election-year confirmation fight over a judge many of them have publicly praised and who would be difficult for them to reject, particularly if a Democrat were to win the November presidential election and they faced the prospect of a more liberal nominee in 2017.

Judge Garland persevered through a lengthy political battle in the mid-1990s that delayed his own confirmation to the United States Court of Appeals for the District of Columbia Circuit by more than a year. Senator Charles E. Grassley, Republican of Iowa, argued at the time that the vacancy should not be filled.

Twenty years later, Mr. Grassley is again standing in the way of Judge Garland’s appointment, this time arguing as chairman of the Senate Judiciary Committee that the next president should be the one to pick the successor to Justice Antonin Scalia, who died suddenly in February.

Judge Garland is often described as brilliant and, at 63, is somewhat aged for a Supreme Court nominee. He is two years older than Chief Justice John G. Roberts Jr., who has been with the court for more than 10 years. The two served together on the appeals court and are said to be friends.