The Board will vote on one of two resolutions calling a special election, in which San Mateo County residents would elect a replacement for Church by June 7, 2011.
The difference between the two resolutions is the mode of the special election, whether it will be conducted using polling places, or whether it can be held using all-mailed ballots, Chief Deputy County Counsel Debra Carlson said.
The Board is also expected to set an election date, Carlson said, which will determine the deadline for possible candidates to file their eligibility papers at the Elections Office.
"Once they know what date is picked they'll know what the filing deadlines will be," Carlson said.
Holding a special election using polling places would cost the county about $1.6 million, Elections Manager David Tom said, whereas an all-mailed election would cost around $1.1 million.
Church, who was elected Assessor-County Clerk-Recorder on Nov. 2, is just over two years into his third term as county supervisor.
Church is expected to attend today's Board meeting and will be allowed to cast his vote on how the special election will be called, Carlson said.
The first supervisorial district encompasses South San Francisco, San Bruno, Millbrae, San Francisco International Airport, Burlingame, and Hillsborough, though all San Mateo County residents are able to vote for supervisors in each of the county's five districts.