EVERETT — A political campaign to raise the sales tax in Snohomish County for public-safety needs reaped a half-million dollars in pledged donations last month.

The Stillaguamish Tribe of Indians made the biggest commitment to A Safer Snohomish County, promising $400,000. Stillaguamish Chairman Shawn Yanity said he and other tribal leaders want to see more deputies on the streets and more social services to lessen the impacts that mental illness, addiction and homelessness are having on the criminal justice system.

“Policing isn’t the answer, but it’s part of the solution,” Yanity said.

The campaign commitments are sure to help county leaders broadcast their message between now and Aug. 2 as they seek to convince voters to support a 0.2 percent sales-tax hike.

If passed, Proposition 1 would add 2 cents to a $10 purchase everywhere in the county, starting Jan. 1.

The increase would generate an estimated $25 million per year in new revenue. County government would receive 60 percent of the total and cities would receive 40 percent divvied up on a per-capita basis.

Sheriff Ty Trenary said he would use part of the money to hire 35 new sheriff’s deputies during the next three years. The money also would pay for hiring at least four more social workers who would be embedded with sheriff’s patrols. There are two social workers performing that kind of duty now.

“The most expensive option is taking people who are fighting an addiction and booking them in the jail and having them serve a short sentence and booking them over and over again,” Trenary said. “I certainly believe in holding people accountable, but if the underlying problem is addiction, then that doesn’t solve the problem.”

County Executive Dave Somers’ office has warned of possible budget cuts if the tax doesn’t pass. Public safety functions, which take up 75 cents of every dollar in the county’s operating budget, would take the biggest hit. Patrol and jail functions overseen by the sheriff stand to lose about $2.8 million in that scenario.

The new sales tax, however, would come in an area that already has some of the highest rates in Washington. Mill Creek’s 9.9 percent is tops in the state. Several other local cities are right behind at 9.8 percent: Edmonds, Mukilteo, Lynnwood, Mountlake Terrace, Brier and the part of Bothell in Snohomish County.

The countywide criminal justice sales tax would come on top of the 0.1 percent sales tax that Mill Creek and Monroe already collect for criminal justice.

The Stillaguamish Tribe, headquartered in the Arlington area, has been a consistent donor to the sheriff’s office and public safety agencies in Arlington and Granite Falls. Tribal money has paid for police cars, fire trucks and thousands of decks of playing cards featuring cold cases. The tribe also has teamed up with county deputies to fight property crimes and youth drug problems.

“We have a great working relationship with the sheriff’s office,” Stillaguamish Police Chief Joe Orford said.

Orford’s department has nine commissioned officers, whose jurisdiction overlaps with county deputies.

Like their colleagues elsewhere, tribal police are seeing a rise in property crimes they attribute to heroin users trying to feed their habit.

“There’s no way we can arrest ourselves out of this situation,” Orford said. “It’s a mental-health issue, it’s an addiction issue. So we’re looking at more of wrap-around services.”

The tribe’s contribution to the sales-tax campaign comes on top of $100,000 promised by the union that represents sheriff’s deputies. Individual donations to the campaign — most from people working in the county criminal justice system — total about $1,600, according to state campaign-finance disclosures.

The campaign has reported spending more than $40,000. Much of that went to pay Seattle-based political firm Strategies 360 for research, including a poll the campaign has declined to release.

The campaign also has hired Brooke Davis, a political consultant who has worked for U.S. Rep. Rick Larsen and other Democrats. Davis said the Stillaguamish Tribe’s donation will help pay for radio ads, direct mail and robocalls.

“Those resources are critical in such a short window,” she said.

The Auditor’s Office plans to mail ballots on July 14.

Noah Haglund: 425-339-3465; nhaglund@heraldnet.com. Twitter: @NWhaglund.