Antonio Villaraigosa won't run for US Senate

LOS ANGELES -- Former Los Angeles Mayor Antonio Villaraigosa says he won't run for Barbara Boxer's Senate seat.

Billionaire climate activist Tom Steyer has also opted not to run for Senate, which leaves state Attorney General Kamala Harris as the only major candidate in the contest after Boxer announced in January that she would not seek re-election in 2016.

Harris has rolled out hard-to-miss endorsements from Los Angeles municipal unions.

Villaraigosa, 62, did not say whether he plans to run for governor.

Lt. Gov. Gavin Newsom also weighed a run for Boxer's seat but then announced plans to run for governor.

The Associated Press and City News Service contributed to this report.