Former U.S. Surgeon General Richard Carmona is running for U.S. Senate, seeking to replace Sen. Jon Kyl.

Kyl is not seeking re-election.

Carmona is registered as an independent, but his campaign said he's running as a Democrat.

He made the announcement today in a press release. He told Arizona Public Media in September he was hesitant to get in the race without knowing whether U.S. Rep. Gabrielle Giffords would run. The point of contact on his news release is Giffords' former campaign manager, Rodd McLeod.

Carmona was a trauma surgeon in the Army and deputy sheriff and surgeon for the Pima County Sheriff's Department, according to the news release announcing his candidacy.

In the statement, Carmona says he wants to bridge partisan politics and that he'll make a more formal announcement in person later this year.

He joins Democrat Don Bivens, who entered the race in July, and Republicans U.S. Rep. Jeff Flake, and developer Wil Cardon.