Democrats were poised to pick up a competitive Assembly seat as San Ramon school-board member Joan Buchanan led Republican Abram Wilson early Wednesday, likely dashing the GOP's last hope of retaining a partisan office in the Bay Area.

With 100 percent of precincts partially or fully reporting, Buchanan had 53 percent of the vote to Wilson's 47 percent. Buchanan's lead over Wilson, the San Ramon mayor, came after labor and business interests spent $1.5 million in the competitive district that stretches from Livermore to Elk Grove.

Termed-out Republican Guy Houston represented the district for the last six years, but voter registration there shifted from GOP to Democratic in 2006. Wilson was vying to become the first black Republican to serve in the Legislature in 75 years, but he struggled to overcome his registration disadvantage in a Democratic year. Houston's seat represented the GOP's last toehold in the deep-blue Bay Area.

In two other local legislative races that were considered competitive, Democrat Lois Wolk defeated Republican Greg Aghazarian in the 5th Senate District, while a local Assembly contest remained too close to call early Wednesday.

Wolk and Aghazarian, both sitting assemblymembers, each raised roughly $1.6 million in their fight to succeed Democratic Sen. Mike Machado, who left due to term limits. The district, which includes Yolo County, a swath of San Joaquin County and parts of Solano County, has traditionally been one of the state's most competitive battlegrounds.

But Wolk, a former Davis mayor, had little problem beating Aghazarian, a Stockton businessman. With 93 percent of precincts reporting in the 5th Senate District, Wolk had 64 percent of the vote to Aghazarian's 36 percent.

In the 10th Assembly District, Republican Jack Sieglock led Democrat Alyson Huber early Wednesday. Organized labor poured money into Huber's campaign to help Democrats compete for the seat held by termed-out Republican Alan Nakanishi.

Sieglock, a former San Joaquin County supervisor, maintained a lead early Wednesday. With 99 percent of precincts partially or fully reporting, Sieglock had 47 percent of the vote, while Huber had 46 percent. Libertarian Janice Bonser had 7 percent.

In other local districts:

-- Yolo County Supervisor Mariko Yamada moved up to the state Assembly in the 8th District. After winning an expensive primary fight against West Sacramento Mayor Christopher Cabaldon, Yamada had an easier general election path in the Democratic district. With 73 percent of precincts reporting, Yamada had 65 percent of the vote to Republican Manuel Cosme's 35 percent.

-- Yuba County Supervisor Dan Logue moved to the Legislature in the 3rd Assembly District. With 96 percent of precincts reporting, Republican Logue had 56 percent of the vote to 44 percent for Democrat Michael "Mickey" Harrington, president of the Butte-Glenn Labor Council.

-- Former lawmaker Jim Nielsen will return to the Legislature after 20 years. With 99 percent of precincts reporting in the 2nd Assembly District, Republicam Nielsen had 65 percent of the votes and Democrat Paul R. Singh had 35 percent. Nielsen, a former member of the state parole board, served in the Legislature for 12 years and as Senate Republican leader from 1983-87. He left the Capitol before the term-limits law took effect in 1990.

-- Republican Assemblyman Roger Niello of Fair Oaks easily won a third two-year term. With 100 percent of precincts reporting, Niello had 54 percent of the vote, compared to Democrat Dan Leahy's 38 percent. Karen Martinez of the Peace and Freedom Party had 6 percent. The 5th District traditionally has included some of the reddest areas of Sacramento County - including Fair Oaks, Folsom and Granite Bay.

-- State Sen. Dave Cox easily won a second four-year term in the upper house. With 100 percent of precincts reporting, Cox had 62 percent of the vote to 38 percent for Democrat Anselmo Chavez. Cox, of Fair Oaks, has served in elective office in Sacramento County - SMUD board, Board of Supervisors, state Assembly and state Senate - for 20 years, a huge advantage in a district that is also heavily Republican.

-- Assemblyman Dave Jones easily won a third term in the 9th district. With 100 percent of precincts reporting, Jones had 73 percent of the vote to 21 percent for Republican Mali Currington. Peace and Freedom candidate Gerald Frink had 6 percent. Jones, a former Sacramento city councilman, entered the campaign with his Democrats holding close to a 3-to-1 lead in voter registration.

-- Assemblyman Ted Gaines, R-Roseville, was unopposed in his re-election win.