San Francisco Mayor Gavin Newsom announced that he has filed paperwork to explore a run for Governor of California in 2010.The good-looking Mayor of San Francisco was re-elected in 2007 with ony token opposition and has used the marriage equality issue to raise his national profile among progressives and Democrats.The record of mayors becoming Governor is not a good one.Interestingly, both of Newsom's most talked-about rivals for the governorship are current or former mayors. Mayor Antonio Villaraigosa of Los Angeles shares extremely vocal gay rights support and marital infidelity with Newsom.Current California Attorney General Jerry Brown served ...