A former Arizona Democratic Party chairman is officially running for his party's nomination for the U.S. seat that Republican Jon Kyl plans to vacate when he retires.

Don Bivens announced his candidacy Monday, saying he wants to provide problem-solving leadership lacking in Washington.

The 59-year-old attorney and Paradise Valley resident told reporters he's "running to win" and is not a stand-in for Rep. Gabrielle Giffords, a fellow Democrat. He says he probably wouldn't have entered the Senate race if he thought Giffords would do so.

Giffords is undergoing rehabilitation after being wounded in a January shooting in Tucson and has not announced her own political plans.

In Bivens' words, "She needs time to heal."

U.S. Rep. Jeff Flake is among several Republicans running for their party's nomination.