Evans in Washington: Former Washington Republican governor Dan Evans has emerged as the leading contender to fill the Senate vacancy created by the death of Sen. Henry M. Jackson, a Democrat, and a state attorney general's advisory opinion yesterday appears to give Republicans an advantage in holding on to the seat until 1988.

Evans, 57, is to meet today with Gov. John Spellman (R) who is expected to offer him the Senate seat, and friends said Evans is leaning toward accepting the appointment, if offered.

The advisory opinion calls for an election on Nov. 8 to fill out Jackson's unexpired term, which runs until 1988. In addition, Attorney General Ken Eikenberry said there should be no primary election and that the winner would be determined by a plurality vote.

This would give the popular Evans a significant advantage not only because he is well known but also because he probably would face several Democratic candidates who would split the Democratic vote. Evans retired after three terms as governor in 1976 and has served since as president of Evergreen State College in Olympia.

Possible Democratic candidates include Seattle Mayor Charles Royer, Reps. Don Bonker, Norman D. Dicks and Mike Lowry, as well as former transportation secretary Brock Adams.

A spokesman for Spellman said yesterday that the governor would take no action until after Jackson's funeral today, but said filling the vacancy is a top priority. Rep. Joel Pritchard is said to be the other Republican prospect.