It is only nicknamed the Sore Loser Rule. State law is more circumspect when it says that the only people in the state who cannot become an official write-in candidate are the ones who just lost the primary for that office.
Obviously any voter can write in any name for any office. But elections officials are only obligated to count votes for “official” write in candidates – those who file paperwork with the elections offices. And the recent losers are prohibited from being official write-in candidates so any votes for them aren’t counted.
Here’s the state law:
Write-in voting — Candidates, declaration.
Any person who desires to be a write-in candidate and have such votes counted at a primary or election may file a declaration of candidacy with the officer designated in RCW 29A.24.070 not later than the day before the primary or election. Declarations of candidacy for write-in candidates must be accompanied by a filing fee in the same manner as required of other candidates filing for the office as provided in RCW 29A.24.091.
Votes cast for write-in candidates who have filed such declarations of candidacy and write-in votes for persons appointed by major political parties pursuant to RCW 29A.28.021 need only specify the name of the candidate in the appropriate location on the ballot in order to be counted. Write-in votes cast for any other candidate, in order to be counted, must designate the office sought and position number or political party, if the manner in which the write-in is done does not make the office or position clear.
No person may file as a write-in candidate where:
(1) At a general election, the person attempting to file either filed as a write-in candidate for the same office at the preceding primary or the person’s name appeared on the ballot for the same office at the preceding primary;
(2) The person attempting to file as a write-in candidate has already filed a valid write-in declaration for that primary or election, unless one or the other of the two filings is for the office of precinct committeeperson;
(3) The name of the person attempting to file already appears on the ballot as a candidate for another office, unless one of the two offices for which he or she is a candidate is precinct committeeperson.
The declaration of candidacy shall be similar to that required by RCW 29A.24.031. No write-in candidate filing under this section may be included in any voter’s pamphlet produced under chapter 29A.32 RCW unless that candidate qualifies to have his or her name printed on the general election ballot. The legislative authority of any jurisdiction producing a local voter’s pamphlet under chapter 29A.32 RCW may provide, by ordinance, for the inclusion of write-in candidates in such pamphlets.
Write-in-voting — Voter intent.
(1) In all cases of write-in votes the canvassing board shall exercise all reasonable efforts to determine the voter’s intent. Write-in votes in the general election are not to be counted for any person who filed for the same office as either a regular or write-in candidate at the preceding primary and failed to qualify for the general election. If a write-in declaration of candidacy has been filed, the voter need only write in that candidate’s name in order for the vote to be counted; the candidate’s party preference does not impact whether the write-in vote shall be counted. If no declaration of write-in candidacy has been filed, the voter must write in the name of the candidate and, if the office or position number cannot be determined by the location of the write-in on the ballot, the office and position number, in order for the write-in vote to be counted.
(2)(a) If a write-in candidate for partisan office does not file a write-in declaration of candidacy but does qualify for the general election ballot, the candidate has not stated a preference for a political party and therefore shall have “(states no party preference)” printed on the general election ballot.
(b) If a write-in candidate for partisan office files a write-in declaration of candidacy and qualifies for the general election ballot, the party preference stated on the write-in declaration of candidacy, if any, shall be printed on the general election ballot.