The Bay Bridge retrofit contractor's new spokesman is a political public-relations heavy hitter with a national reputation for digging up dirt on embattled clients' critics. Chris Lehane, 37, helped the Clinton White House spin the Whitewater investigation, spoke for Vice President Al Gore on the 2000 presidential campaign trail and advised former Gov. Gray Davis during the 2001 energy crisis and 2002 gubernatorial campaign. Now he's working for KFM Joint Venture, the contractor building the Bay Bridge's new eastern span. The Oakland Tribune has reported welders' accusations that many of the project's welds are defective and that unsafe working conditions...