California administers what is widely considered the nation's most difficult bar examination twice each year, in February and July. Several prominent attorneys and politicians have either never passed, or had difficulty passing, the California Bar Exam. Significant among these are former Los Angeles Mayor Antonio Villaraigosa (a graduate of Peoples College of Law who never passed the bar exam after failing four times), Stanford law professor Kathleen Sullivan (Harvard Law School) (who failed the bar in July 2005 but passed on her second attempt in February 2006), California Governor and former Attorney General Jerry Brown (Yale Law School, '64) (who took it twice before passing) and former California Governor Pete Wilson (UC Berkeley School of Law) (who passed on his fourth attempt). Unsuccessful applicants have even sued the State Bar—unsuccessfully—on the grounds that the exam is unnecessarily difficult.