SAN FRANCISCO - Last week's state Senate vote seeking to legalize gay marriage is the latest example of the political schizophrenia that has come to define the issue in the nation's most populous state. Since 1999, when lawmakers established a registry of same-sex couples, California has been in the vanguard of extending to gay and lesbian partners nearly all the rights enjoyed by heterosexual couples. But for all the state's live-and-let-live social tolerance, voters have balked at granting gay couples the right to marry. In 2000, California voters overwhelmingly approved Proposition 22, which strictly defined marriage as the union of...