John D. Fabian: The paradox of elected judges: Tension in the American judicial system, The Georgetown Journal of Legal Ethics (Fall 2001) reports a highly publicized judge election but still with only 18.6% turnout.
This is not unusual. As far as we can tell, voter turnouts for US judicial elections usually range from 10% to 29%, and mostly 10-15%. A study of this (pdf) by www.seventy.org claimed that approximately 13% of Pennsylvania voters qualify as "judicial voters." They claimed that voters often try but fail to get information on judges because there is a "dearth" of it. They claim that the political party and geography were among the most important "factors" used to decide on judges by members of "focus groups." However, in many places, judges are (by law) not identified by party affiliation exactly to prevent robot-like party-line voting.
(Incidentally, this did not stop judges from collecting enormous campaign contributions, largely from attorneys and those appearing before them in court, and including for judges in uncontested "races," say the AJS.)