(Salem, OR)  --  A new Rasmussen Reports opinion poll on Oregon's U.S. Senate race shows Democratic incumbent Jeff Merkley with a ten-point lead over GOP challenger Monica Wehby.  The tally is 47-percent in favor of Merkley, 37-percent favoring Wehby, five-percent preferring another candidate, and eleven-percent undecided.  The poll was taken among 750 likely voters on May 21st and 22nd, following the recent primary elections.