SEATTLE (AP) — The campaign to legalize and tax marijuana for adults in Washington state is rolling as next month's vote approaches, with more than $1 million in new contributions reported since last week and a surprising endorsement Wednesday from Republican U.S. Senate hopeful Michael Baumgartner .

The money, most of it from retired Progressive Insurance founder Peter Lewis , means Initiative 502's backers have raised nearly $4.1 million over the course of the campaign, with $1.2 million left to spend. Alison Holcomb , campaign manager for New Approach Washington, says her group is planning a broader television campaign than the three-week advertising blitz it ran in Western Washington in August.

Meanwhile, Baumgartner's decision to endorse the initiative in an interview with The Associated Press gave the campaign one of its highest-profile Republican supporters yet. Baumgartner, a state senator from Spokane, is running a longshot bid to unseat Democratic U.S. Sen. Maria Cantwell , who came out against I-502 Wednesday afternoon.

Baumgartner said drug law reform isn't typically supported by his party, but he believes I-502 is a good step toward changing what he described as a wasteful policy of marijuana prohibition.

"It's taking a different approach to a very expensive drug war, and potentially a better approach," Baumgartner said. "They've checked all the boxes as far as what you would want to see happen in terms of provisions to keep it away from children and limiting access in the public space. I've just been impressed with the initiative and the people running it."

Asked for her position, Cantwell issued a written statement.

"While I remain a strong supporter of our state's medicinal marijuana laws, I don't believe it should be legalized for recreational purposes based on concerns expressed by law enforcement and the current drafting of the initiative," she said. "Whatever the result, I will honor the will of the voters' decision in November."

I-502 would legalize possession of up to an ounce of marijuana under state law for those over 21. The state would license growers, processors and retail stores, and impose 25 percent taxes at each stage. State analysts have suggested it could bring in hundreds of millions of dollars a year.

The measure, which polls show leading, would also set a blood-test limit for driving under the influence and prohibit public use of the drug.

Marijuana would remain illegal under federal law, and the burning question remains whether the Justice Department would sue to try to block I-502 from taking effect if it passes, on the grounds that it conflicts with federal law. The DOJ could also simply seize any tax revenue as proceeds of illicit drug transactions.

Washington is one of three states, along with Oregon and Colorado, considering legalization measures this year.

I-502 has received high-profile endorsements from former Seattle FBI head Charles Mandigo , former U.S. Attorneys John McKay and Kate Pflaumer (FLAU'-mer), both candidates for sheriff in King County, and the nonprofit Children's Alliance , which argues that drug laws disproportionately hurt minority children.

The initiative's only formal opposition comes from a group representing medical marijuana patients who say the DUI limit is so strict it could prevent them from driving at all, but some other organizations, including the Washington Association of Sheriffs and Police Chiefs, are also opposed.

Steve Freng , of the federally funded Northwest High Intensity Drug Trafficking Area, said he worries about the effect on children, especially on the modeling behavior of parents who might start smoking weed openly in the home if it's legalized.

Baumgartner responded: "That's a concern, but we have to be realistic about what's going on in people's homes today. Usage stays constant regardless of drug policy."

Baumgartner served as a civilian State Department contractor in Afghanistan, where he advised an Afghan counternarcotics team in Helmand Province. He said one of his primary motives in supporting I-502 is to bring the U.S. marijuana trade out of the shadows and regulate it. If elected, he said, he'd support allowing states to draft their own drug laws "in a responsible manner."

He said he hoped voters who care about the issue would appreciate his taking a stand.

"I really don't know the direct political ramifications," Baumgartner said. "I always think if you get the policy right, the politics will follow."

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Johnson can be reached at https://twitter.com/GeneAPseattle