Horn had 54.12 percent of the vote in the Board of Supervisors District 5, compared to opponent Steve Gronke's 45.8 percent of the vote( 57 percent of the precincts counted). Gronke is a member of the Vista City Council.
In the county's District 4, Roberts had 58.62 percent of the vote to American Red Cross spokesman Stephen Whitburn's 41.38 percent, with 47 percent of the precincts counted.
Horn and Roberts -- who sit on the board with Greg Cox, Dianne Jacob and Pam Slater-Price -- are the first supervisors in 12 years to be forced into a runoff election. The board has remained unchanged since 1995.
During their respective races, both incumbents pointed to the fiscal discipline exhibited by the board and county administrators, noting that while San Diego County has reduced spending and laid off employees during the economic downturn, the cuts have not been as severe as those made by other government bodies.