LOS ANGELES (AP) - A dozen candidates are vying to fill a vacant U.S. House seat in a race that has highlighted Southern California's shifting racial landscape.

The 32nd Congressional District seat - held by Rep. Hilda Solis until she resigned to become President Barack Obama's labor secretary - has been in Hispanic hands since the 1980s.

Two of three people in the heavily Democratic district are Hispanic, as are about half the voters. Yet one of the two leading candidates in the race is Asian, former state Assemblywoman Judy Chu. She is in a tight race with fellow Democrat Gil Cedillo, a Hispanic state senator.

The contest will test whether residents are willing to overlook racial and ethnic identity at the ballot box, which for years has shaped politics in the heavily Democratic district east of Los Angeles.

The ballot includes 12 candidates - eight Democrats, three Republicans and a Libertarian. It's unlikely any candidate will get the required majority to win outright on Election Night. If no candidate clears that mark, the top finishers in each party will advance to a July 14 runoff.

The Democrat will be the all-but-certain winner of a runoff in a district where the party holds a more than 2-to-1 registration edge over Republicans.

White voters are a sliver of the electorate but could provide a decisive margin in what's expected to be a low-turnout election.

The district's population is about 64 percent Hispanic, 20 percent Asian, 12 percent white and 2 percent black.

Endorsements have cut across racial and ethnic lines. Chu, a member of the state Board of Equalization, and Cedillo have stressed an ability to work on behalf of various groups.

By Michael R. Blood