Mayor Antonio Villaraigosa slipped quietly out of the city last week to campaign in Iowa for Sen. Hillary Rodham Clinton, a rare public foray into presidential politics since his marital meltdown dominated front pages last summer. Clinton made a splash in May when she snagged the Democratic mayor's endorsement, and even former President Bill Clinton was called in to help lock up Villaraigosa's support. The New York senator said at the time that Villaraigosa, one of the nation's most prominent Hispanic politicians, would be "reaching out to a broad range of voters across the country." In other states prominent supporters...