Florida Senator Marco Rubio has withdrawn his support for the nomination of an African-American openly gay federal judge.

Rubio supported President Barack Obama's decision to nominate Judge William Thomas to the Federal District Court for the Southern District of Florida, first announced in November.

(Related: Obama nominates William Thomas to federal bench.)

A Rubio spokesperson told The New York Times that the junior senator is questioning Thomas' “fitness” for the bench.

“Those concerns include questions about his judicial temperament and his willingness to impose appropriate criminal sentences,” the spokesperson said.

A nomination cannot proceed without the support of both U.S. senators from a nominee's home state. That is, without Rubio's support, William's nomination is effectively blocked.

“As much as I would like to think that politics has nothing to do with this, it looks as if it does,” Yolanda Strader, president of Miami's largest association for black lawyers, told the Times. “It would be unfair to prevent a well-qualified judicial nominee from proceeding with the nomination process because he is an openly gay black male.”