The ballot measure was winning by just 43 votes Tuesday as officials in King County resumed counting votes. There also likely are hundreds more votes to be counted in the coming days due to the lengthy ballot-collection process caused by the state's vote-by-mail system.
On election night, the initiative jumped out to a 261-vote margin - a decent gap in a race that's likely to draw maybe 6,000 total votes. Supporters declared victory but have since lost much of their advantage, with opponents gaining ground during each ballot drop.
"There's no cork-popping. There's only nail-biting," said Gary Smith, a spokesman with opposition group Common Sense SeaTac.
The campaigns say they also have a list of about 150 voters from SeaTac who had signatures on their ballots that did not match records. Both sides are working to identify voters who might support their cause and contacting them to ensure that they return the paperwork necessary to finalize their ballots.
The race has drawn national interest from both labor unions and business groups, and both sides have spent considerable sums to influence the outcome - enough money, in fact, to hire every registered voter in the city for a day at $15 per hour.
Washington has the nation's highest state minimum wage at $9.19 an hour; the federal minimum wage is $7.25 per hour.
Heather Weiner, a spokeswoman for the campaign to support the initiative, said the two sides likely have talked to every voter in the city at least once in recent months. Because of that, the campaigns know which way the problematic ballots are leaning.
"It's a very small population of voters," Weiner said.
Weiner suspects that unless the voter has died or moved out of the state, the campaigns will make sure any problematic ballots get counted in the end.
Other ballots in which the voter's intent is in question also will be resolved during a canvassing process in the coming days.
The campaigns will have the option of seeking a recount, as long as they pay the cost of conducting it. Weiner said she suspects either side will request a recount if the final tally shows a margin of just a couple hundred votes.