(Salem, OR)  --  A new opinion poll shows Governor John Kitzhaber maintaining the lead in his bid for election to a fourth term in office.  Kitzhaber, the Democratic incumbent, has a 48-percent-to-38-percent lead over his GOP challenger, Dennis Richardson.  The Rasmussen poll, commissioned by KATU-TV, has a margin of error of plus-or-minus four percent.  The survey's results are close to those of a Survey USA poll taken last month, which showed Kitzhaber leading by 48 percent to 36 percent.