Washington’s initiative season is open, and much of the early attention is on an attempt by initiative activist Tim Eyman to use a heavy hammer to persuade lawmakers to submit a constitutional amendment to require a two-thirds supermajority for all taxes passed in Olympia.

The hammer? If his Initiative 1325 qualifies for the ballot and passes this fall, it would impose an annual $1 billion cut in the state sales tax if legislators refuse to put the constitutional amendment on the ballot for public vote in 2015.  Eyman told reporters at the Secretary of State’s Office on Monday that “It’s hardball — a billion reasons to let people vote on this. It’s a strong financial incentive.”

Voters have approved the supermajority requirement as part of five previous initiatives. Legislators sometimes suspended the requirement and other times did not try to raise taxes.  Last year, the state Supreme Court said the supermajority requirement violates the state constitution, which says a bill (or tax) becomes law if it gets a majority vote in both chambers and the governor’s signature.

The only way for Eyman to get the supermajority requirement would be to amend the state constitution — something that cannot be done by initiative. The Legislature must originate any amendment. Passage takes two-thirds of both houses, plus a majority vote at the next general election.

Eyman said polling continues to show broad public support for the concept of the supermajority requirement and even stronger support for the idea of letting people vote on a constitutional amendment.  Democrats have resisted, particularly since the state Supreme Court has ordered the Legislature to boost state aid to education by billions.  Lawmakers added roughly $1 billion in the current budget.

It takes 246,372 valid voter signatures to qualify an initiative to the ballot — and more than 320,000 are suggested to cover invalid and duplicate signatures. Deadline is July 3.

Eyman also filed initiatives mandating $30 car tabs and dealing with red light traffic cams, but said he will put his energy into the tax measure.