Republican attorney Catharine Baker topped the ballot in Tuesday's primary in the 16th State Assembly District, which includes Pleasanton, winning 21,270 votes, or 36.5% of all votes cast in the assembly race.
Dublin Mayor Tim Sbranti finished second with 17,270 votes, or 29.6% of the votes cast.
Two other Democrats in the race trailed, with Steve Glazer of Orinda receiving 13,137 votes, or 22.5%, and Newell Arnerich earning 6,651 votes, or 11.4%.
Baker and Sbranti will now compete in a run-off in the General Election Nov. 4.
Baker held the lead shortly after polls closed and mail-in ballots were tallied, falling behind only in Alameda County.
Voting was light most of the day in Pleasanton as precinct workers often sat idle for lack of voters.
The light vote was not a surprise in a mid-term Congressional race and with no City Council or school board races on the primary ballot.
In the 15th Congressional District race, first term Congressman Eric Swalwell held on to an early lead, garnering 28,292 votes, or 49.2% of all votes cast in that race, well ahead of challengers Hugh Bussell and State Senator Ellen M. Corbett.
Hugh Bussell, the only Republican in the race, finished second with with 14,901 votes, or 25.9%, with Corbett trailing with 14,291 votes, or 24.9% of the total.
Bussell, a Livermore resident and technology manager/educator, is vice chair of the Alameda County Republican Party and is employed by Workday in Pleasanton.
Under California's open primary format, the two candidates who emerged with the most votes, regardless of political party affiliation, move on to the November election, which means Swalwell, the Democrat from Dublin, and Bussell the Republican facing off again in November.