Iowa's jet-setting governor, Tom Vilsack, appeared at a news conference in San Francisco, California, this morning -- with the city's mayor, Gavin Newsom -- to speak in support of one of the propositions on California's November ballot. Proposition 87 seeks to impose a tax on oil production and funnel the money to produce "alternative" forms of energy. Former President Bill Clinton appeared in California last Friday to speak in favor of the move. Actress Geena Davis of "Thelma and Louise" fame was at that news event with Clinton. Former Vice President Al Gore has cut a commercial for "Yes on Prop 87" campaign. Actress Julia Roberts appeared at an event on Monday to laud the initiative.