Candidates must live in District 1, which includes South San Francisco, San Bruno and Hillsborough, but the election is held county-wide.
While it's a mail-only election, voters can vote in person at a county elections office: 40 Tower Road in San Mateo, or 555 County Government Center in Redwood City. Mail-in ballots may be dropped off at any city hall in the county during regular business hours.
Ballots must be received by the county by 8 p.m. Tuesday, May 3.
The candidate who receives the most votes will be elected to fill the remainder of Mr. Church's term, which ends in January 2013.
For more information, go to:
• SmartVoter.org (the League of Women Voters site).
• shapethefuture.org (the county elections office site).