SAN DIEGO -- Incumbents dominate most of the state legislative races before San Diego County voters Tuesday, but term limits have led to a contested race in the South Bay.

Democrats are gunning to reclaim the 78th Assembly District, held by a Republican since 2002. Assemblywoman Shirley Horton, R-Chula Vista, cannot seek reelection because she is termed out.

Vying for the Democratic spot on the November ballot are Auday Arabo, a small-business advocate and former Republican; Marty Block, president of the San Diego Community College District; Arlie Ricasa, a Sweetwater Union High School District board member; and Maxine Sherard, a retired professor.

Republican John McCann, a member of the Chula Vista City Council and businessman, is running unopposed by his party. Geof Gibson is the lone Libertarian on the ballot.

The district stretches from San Diego to Chula Vista and includes the cities of Spring Valley, Lemon Grove and parts of Bonita.

In the 75th Assembly District, Republican Nathan Fletcher, a businessman, is looking to succeed Assemblyman George Plescia, R-La Jolla, who is being forced out of office due to term limits. Fletcher is the only Republican on the ballot in that race.

Also running is Democrat Darren Kasai, a small business owner, and Libertarian John Murphy, a businessman.

The 75th District includes the communities of Escondido, Poway, San Diego, La Jolla, Mira Mesa, Scripps Ranch, Rancho Santa Fe and Rancho Bernardo.

In the 74th Assembly District, incumbent Assemblyman Garrick Martin, R-Solana Beach, is the only Republican on the ballot. Attorney Brett Deforest Maxfield is the only Democrat. Paul King, a small business owner, is the single Libertarian on the ballot.

The district includes Carlsbad, Del Mar, Encinitas, Escondido, Oceanside, San Marcos, Vista and parts of San Diego and Rancho Santa Fe.

Assemblywoman Lori Saldana, D-San Diego, is the incumbent in the 76th Assembly District, which includes much of the central and northern portions of the city of San Diego.

Republicans vying for a place on the November ballot include business manager Ralph Denney and retired physician assistant Kim Tran. Daniel Baehr, a school bus driver, is running as a Libertarian.

The 77th Assembly District seat is held by Assemblyman Joel Anderson, R-El Cajon. Raymond Lutz, an engineer, is the sole Democrat on the ballot. Small business owner Richard Belitz is the lone Libertarian.

The district includes El Cajon, La Mesa, Santee, Jamul, Lakeside, Ramona, Borrego Springs and parts of San Diego.

Assemblywoman Mary Salas, D-Chula Vista, is being challenged by Jesse Albritten, a tax consultant, for the Democratic spot on the November ballot for the 79th State Assembly District. Fraud investigator Derrick Roach is the only Republican on the ballot. Randolph Myrseth is the sole Libertarian.

The district includes Imperial Beach, Chula Vista, Coronado, National City, Otay Mesa and San Ysidro.

Sen. Christine Kehoe, D-San Diego, is the only Democrat on the ballot in the 39th Senate District, which stretches from Del Mar to downtown San Diego and east to Spring Valley. Small business owner Jeff Perwin is the single Republican on the ballot. Test systems designer Jesse Thomas is the only Libertarian.