State Sen. Richard Alarcon, who finished a distant fifth place in the March 8 election for Los Angeles mayor, plans to announce his endorsement of City Councilman Antonio Villaraigosa for the city’s top job, an aide said.

Villaraigosa, who finished first in the primary, faces incumbent James Hahn in the May 17 runoff election.

Alarcon, a Van Nuys Democrat, won 3.6 percent of the vote for mayor, mostly in his northeastern San Fernando Valley base. The area favored Villaraigosa over Hahn in the primary vote.

Alarcon planned to announce his endorsement of Villaraigosa at a meeting of the Los Angeles County Democratic Party on Tuesday evening, an aide to the senator said. Alarcon met separately with Hahn and Villaraigosa last week.

Hahn and Villaraigosa are vying for the endorsements of the remaining candidates, former Assembly Speaker Bob Hertzberg and L.A. City Councilman Bernard Parks. Neither has yet endorsed a runoff candidate.