WASHINGTON STATE – Come Monday, Washington is expected to have a state income tax on the books for the first time in nearly a century.

Then what?

A legal challenge certainly, maybe two. A ballot battle as well, its timing less certain.

Opponents of the much-debated 9.9% tax on households with incomes above $1 million a year are honing legal and electoral strategies to invalidate and repeal legislation that Gov. Bob Ferguson is expected to sign Monday.

Their specific tactics will become public in the coming days. It’s unlikely any will surprise those engaged in the spirited discourse on the controversial “millionaires’ tax” since its emergence last fall.

Supporters will celebrate when Senate Bill 6346 becomes law. But don’t expect them to launch anything resembling a statewide victory tour. The tax will need to clear formidable hurdles before collections could actually begin in 2029, as planned.

“There’s a legal fight and a public relations battle shaping up on day one,” said Sandeep Kaushik, a partner with Sound View Strategies, a Seattle-based political consulting firm. “The signing of the bill is just the start of it.”

History isn’t on the tax’s side. Voters approved an income tax in 1932 only to have it tossed out a year later by a divided state Supreme Court. Since then, voters have rejected variations of the idea multiple times, most recently in 2010 when the income level was $200,000.

As a result, Washington has been one of nine states that does not tax individual wage and salary income.

Courtroom brawling

Opponents are expected to swiftly file a lawsuit challenging the constitutionality of the new law, citing the 1933 court ruling, according to multiple people familiar with the strategy. Rob McKenna, a former state attorney general and 2012 Republican candidate for Washington governor, is among those formulating the arguments.

Plaintiffs in this suit will likely be owners of small companies and family businesses, and tech entrepreneurs, not celebrity millionaires who’ve publicly opposed the income tax.

This suit, in which the state is the defendant, would be filed in a county superior court. Regardless of the lower court ruling, the parties involved would appeal directly to the state Supreme Court to resolve the constitutional question quickly.

A lawsuit to take down the tax entirely may not be the first legal maneuver.

Some opponents might also try to knock off the so-called “necessity clause,” which shields the legislation from a referendum. If successful, tax foes would gain that option for asking voters in November to repeal the law.

A referendum would require turning in roughly 200,000 voter signatures by June 10 to qualify for the ballot. As it stands, an initiative is the only path for voters to undo the law. This would require twice as many signatures to qualify.

Will it reach ballots this year or next?

Within the ranks of the coalition fighting the income tax, there’s debate on whether to pursue an initiative this year or wait until 2027.

Getting an initiative to roll back the tax on the November ballot would be a Herculean task.

It would require collecting and turning in signatures of at least 308,911 voters by 5 p.m. on July 2. The secretary of state’s office recommends submitting close to 400,000 signatures to account for invalid ones.

Signature gathering would likely not start for several weeks if, as expected, tax supporters undertake a time-consuming court duel on how the measure is described on ballots.

While time would be tight, Brian Heywood, founder of Let’s Go Washington, and Jim Walsh, chair of the state Republican Party, say getting the measure on the ballot this year can and should be done.

Re-energizing voters a year from now won’t be easy, they said.

“It’s crazy to wait,” said Heywood, whose political committee has qualified nine initiatives in the past three years. Its measures concerning parental rights and barring transgender athletes from girls’ sports are already on the November ballot.

Walsh acknowledged some in the opposition coalition want to hold off, but said, “the issue is on people’s minds now.”

“We should strike while the iron is hot,” he said.

He also said there will be a beneficial synergy as Republican candidates running this year seize on the income tax as a campaign issue.

“I think 2026 is the better play,” he said.

If opponents wait until 2027, they will have until the end of this year to collect 308,911 signatures for a slightly different path: an initiative to the Legislature. If successful, it would first go to state lawmakers to consider adopting and, if they don’t, wind up on the November 2027 ballot. Such an initiative has been filed, but it’s too soon for petitions to be circulated.

Proponents of this approach say one benefit is to see how the legal challenge plays out.

They also worry about political headwinds this fall.

Democrats are energized for the 2026 midterms across the country, due in part to the unpopularity of President Donald Trump and his policies. Though the state income tax is a hot topic now, when ballots go out, Democratic voters may be swayed to preserve a law put in place by their party.

Next year, the electorate will likely be more conservative, the turnout lower and few if any state or federal offices on the ballot, all of which would tend to favor an anti-tax measure.

There are business leaders and political conservatives who want to avoid a repeat of 2024. That’s when voters rejected Let’s Go Washington-backed measures to repeal or rework the state’s capital gains tax, its cap-and-trade program, and a long-term care services tax.

Supporters of waiting until 2027 to pursue an initiative declined to go on the record while the conversation on tactics plays out.

Kaushik, who helped steer the opposition campaign to the 2024 measures, agreed that the “political tide” is rising for Democrats in 2026.

“If I was them, I wouldn’t be running an initiative,” he said of the income tax foes.

Peter Graves of the 76 Group, who’s advised business groups and Republican candidates, described the 2026 versus 2027 debate as a false choice.

“We should run an anti-income tax measure every year until it’s off the table for good,” he said.

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