Four Stanford graduates have become Supreme Court justices since the football team produced its only Heisman Trophy winner, Jim Plunkett, in 1970. Into this yawning gap burst Toby Gerhart, a senior tailback, who has insinuated himself into the Heisman conversation this month while leading Stanford to consecutive upsets of Oregon and Southern California. Gerhart, 22, has stiff-armed convention, critics and convenience while gaining 1,395 yards on 262 carries and scoring 19 touchdowns this season. The Cardinal, which has not won a national title in football since 1926, finished 1-11 in Gerhart’s freshman season. He is on a pace to finish with more than 1,800 yards for Stanford, which hosts cross-bay rival California on Saturday, is 7-3 and guaranteed its first bowl appearance since 2001.