Orange County will hold a special election on March 12 to select a replacement for former Supervisor Todd Spitzer, who left his board post on Monday to become the county’s district attorney.

Several well-known local politicians already have declared their candidacies for the 3rd District board seat. On the Democrat side, the list is down to a single big name, for now: former congresswoman Loretta Sanchez. On the GOP side, the field so far includes Irvine Mayor Don Wagner and former Anaheim Councilwoman Kris Murray.

The March special election – set Tuesday by the four supervisors sitting on the five-member board – could alter the board’s partisan makeup. Recently elected 4th District Supervisor Doug Chaffee, who swore in on Tuesday, is the first Democrat on the board in a dozen years. If Democrats can win in March, the party would have a chance to win a majority in 2020.

In late December, well-funded Democrat businessman Andy Thorburn mentioned party loyalty as a reason when he withdrew from the race to replace Spitzer, saying “it is essential we have a Democrat on the Board.” That leaves Sanchez, the most prominent politician in the contest, as the lone Democrat facing two Republicans.

Republicans hold a 4 percentage point voter registration advantage in the district. But if the current list of candidates holds, the two GOP hopefuls might split support among conservative voters in a way that could help Sanchez. Past special elections for county supervisor have had low turnout and narrow margins, with the last two special contests decided by a combined 50 votes.

The official candidate filing period begins Wednesday and lasts through Jan. 28. Whoever is elected likely would take office on either March 26 or April 9. The new supervisor will serve for 21 months and could seek re-election in 2020.