The public popularity in Washington State of the late Democratic Sen. Henry M. Jackson was almost unparalleled. Only former Gov. Daniel Evans, a Republican, was held in such high esteem by voters here.
Now it would appear that Mr. Evans - who occupies Jackson's seat temporarily - may end up being elected to it.
As the result of the opinion of State Attorney General Ken Eikenberry to hold a special election in November, Democrats are scrambling to find a suitable candidate to buck Evans, who would likely be the front-runner to win the Jackson seat. Evans, appointed by GOP Gov. John Spellman to fill the vacancy, has not only the advantage of brief incumbency but also name recognition stemming from his three terms as governor.
Although reluctant in the past to go to what he calls ''the other Washington, '' Evans plans to run in November to fill the five years remaining in Senator Jackson's term. He has filed to run in a special Oct. 11 primary election.
Evans is the only governor in the history of Washington to serve three consecutive terms, the last ending in 1976. And he has stayed in the public eye as president of Evergreen College in Olympia and as chairman of the Pacific Northwest Regional Power Council, an electric power planning body.
During his service as governor, Evans established a reputation for progressive politics, leading campaigns to reform Washington's tax system, set up a state department of ecology, and reform the state penitentiary at Walla Walla.
Though he's not exactly President Reagan's kind of Republican - he called for the resignation of Secretary of Interior James G. Watt, for example - the administration is said to have supported the Evans appointment, knowing he is probably the most electable Republican in the state. And with control of the Senate at stake in 1984, the administration is not about to turn its back on any electable Republican.
Although the appointment caused some grumbling from the right wing of the GOP , it appears Washington state Republicans will unite behind Evans, giving him little trouble in winning the special primary.
Mr. Evans and Washington Sen. Slade Gorton should form an unusually close team in the Senate. They have been close friends since serving together in the legislature in the 1950s as part of a new wave of moderate Republicans.
This has led to speculation that the two may eventually form the same kind of powerful combination that former Sens. Warren Magnuson and Henry Jackson forged during their long service together in the Senate.
Meanwhile, Jackson's untimely death and the imminent election have caught Democrats flat-footed. They would have preferred an election in 1984, giving them time to sort through candidates, raise money, and line up the support.
As things stand now, a decision whether to run or not must be made by the end of the day today. Seattle Mayor Charles Royer, who will be a candidate, said recently he has only a few hundred dollars in his campaign chest.
One advantage for the Democrats is that because it is an off-year election, incumbent congressmen may run for the Senate without endangering their seats in the House of Representatives. Rep. Mike Lowry of Seattle's Mercer Island has also filed to be a candidate.
The obvious strategy for the Democrats would be to unite behind one of their popular congressmen, but that may be difficult in so short a time.
Washington has a slew of able Democratic congressmen whose ambitions to advance to the Senate have long been frustrated by the fact that former Senators Magnuson and Jackson held the Senate seats in an iron grip for years.
They would all probably defer to Rep. Tom Foley of Spokane if he decided to enter the race, but Mr. Foley may be reluctant to do so because of his leadership position in the House. He is the majority whip, and is considered a potential candidate for Speaker of the House.