IN HIS RECENT and abortive campaign for the mayoralty or the city of New York, the honorable Norman Mailer proved once again that his thinking, though often well intentioned, is nonetheless pitifully deficient in scope. While not without merit, his plan to turn New York City into a separate state of the Union - due to its myriad distinguished attributes - was redeemed mainly by the fact that, in keeping with Mr. Mailer's usual modesty and astute self-appraisal, he implied that he would be available (or the governorship when statehood came to flower. This appetite for public office, of course, is based on the enlightened contemporary concept of total talent: A gifted novelist would obviously be a brilliant statesman; a great fullback could unquestionably play a superb Hamlet; a renowned pediatrician could easily master the complexities of global policy; an incomparable but self-effacing New York humorist, broadcaster, bon vivant and boulevardier is eminently qualified to become - But I'm getting ahead of myself...