Sen. Lamar Alexander, R-Tenn., the No. 3 Republican in the party's Senate leadership, announced his decision Thursday on the floor of the Senate.
"Even though Judge Sotomayor's political and judicial philosophy may be different than mine, especially regarding Second Amendments rights," Alexander said, "I will vote to confirm her because she is well qualified by experience, temperament, character and intellect to serve as an Associate Justice of the United States Supreme Court."
Most Republican senators who have taken a public position on the nomination have said they will oppose Sotomayor, The Washington Post reported. A few moderate Republicans support her.
Alexander said Obama was wrong to oppose President George W. Bush's two Supreme Court nominees -- Chief Justice John Robert and Justice Samuel Alito. He said he wants "to help to return the Senate to the practice only recently lost of inquiring diligently into qualifications of a nominee and then accepting that elections have consequences, one of which is to confer upon the president the constitutional right to nominate justices of the Supreme Court of the United States."