Republican FCC Commissioner Kathleen Abernathy today announced her intention to leave the agency on Dec. 9, when the commission likely will be left with just three members.

Abernathy’s term expired last year, but federal rules permit a commissioner to serve until Congress adjourns the following year if a replacement is not appointed. Combined with former Chairman Michael Powell’s resignation in the spring, Abernathy’s departure could leave FCC Chairman Kevin Martin in the unusual position of being the only Republican on the commission while his party’s president is in office.

President George W. Bush has nominated Tennessee regulator Deborah Tate to fill a Republican slot on the commission and has renominated Democratic Commissioner Michael Copps. Sen. Ted Stevens reportedly has said the Senate Commerce Committee, which he chairs, probably won’t act on Tate’s nomination until after Dec. 12. After that, the nomination would have to be approved by the full Senate, which already is considering nominations for a Supreme Court justice and chairman of the Federal Reserve.

During her four-and-a-half year tenure at the FCC, Abernathy was noted for her philosophy that competitive markets provide greater benefits to consumers than government regulation.

“All of our successes, and even our failures, demonstrate one fundamental truth: that regulation is most effective when it deals with markets as they are—not as they might once have been, and not as we would ideally like them to be,” Abernathy said in a prepared statement. “To the extent the Commission’s decisions on difficult issues in the days to come are based on this principle, it will continue to advance the security and well-being of our country and our people.”