Rick Steves, who built a business empire on his travel guides and public television and radio shows, has a suburban-dad demeanor and an earnest enthusiasm that makes him a natural on PBS pledge drives.

That's why backers of Washington's Initiative 502 were thrilled to have him spend seven days touring the state to pitch voters on what might seem like an unlikely cause for his mainstream fans: passing their ballot measure to legalize marijuana.

"We're joined by doctors, law enforcement professionals and treatment professionals," Steves said at a packed forum in Vancouver. "It's not the kind of stoners you might expect... I-502 does not say marijuana is good. It says prohibition is an expensive, losing battle and we've got to do something different."

Unlike Oregon, where the marijuana legalization measure was drafted primarily to free pot smokers and growers from criminal sanctions, the stricter Washington approach is aimed at wooing middle-of-the-road voters.

Washington's measure is so restrictive that the only organized opposition is from marijuana advocates. They're particularly upset by a tough new drugged-driving provision they say would make it risky for regular marijuana users to ever get behind the wheel.

Marijuana measures

Measures are on the ballot in Oregon, Washington and Colorado:

Possession

Oregon

: No limits on personal possession

Washington

: May possess up to one ounce.

Colorado

: May possess up to one ounce.

Home growing

Oregon

: No limits on for personal use.

Washington

: Home growing not allowed.

Colorado

: May possess up to six plants.

Driving while impaired

Oregon

: Keeps current laws prohibiting driving while impaired by drugs.

Washington

: Imposes strict new standard on amount of active ingredient of marijuana in bloodstream.

Colorado

: Keeps current impairment law.

"It's not legalization at all," fumed Steve Sarich, a medical marijuana advocate. He said he has awakened with more THC – the active ingredient of marijuana – in his bloodstream than the new DUI standard would allow.

Steves and other I-502 advocates say opponents are wrong about the driving provisions. But they make no apologies for writing an initiative designed to sway Joe Six-pack.

"If you want to move marijuana reform forward," said Alison Holcomb, the campaign manager, "you have to meet voters where they are now."

Holcomb, an American Civil Liberties Union lawyer who favors conservative business wear, works out of a Seattle campaign office where you have to look hard to find a marijuana leaf logo.

She's assembled a powerful list of sponsors – including a former U.S. attorney for Washington and the former head of the Seattle FBI office – and big donations from national marijuana reformers for an initiative that was carefully poll-tested.

So far, Holcomb has raised $5.4 million from the campaign, with $1.5 million from Peter Lewis, the billionaire founder of Progressive Insurance who has long sought to legalize marijuana. Another $1.3 million came from Drug Policy Action, a group tied to wealthy financier George Soros. Steves and his company gave $450,000.

The latest poll, released Thursday, shows the measure ahead, 47 percent to 40 percent, among likely voters.

In contrast to Oregon's Measure 80, I-502 would allow people to possess no more than one ounce of marijuana. People couldn't grow marijuana at home – and commercial producers and retailers would be strictly regulated by the Washington State Liquor Control Board. They would face high taxes and some proceeds would be plowed into drug education and prevention programs.

And there is that new drugged-driving standard. It says drivers are presumed to be impaired if they have more than five nanograms of active THC in their bloodstream.

Holcomb said active THC leaves the bloodstream relatively quickly, unlike other pot ingredients that can linger for weeks and often show up in employer drug tests.

The science behind this approach is hotly disputed, with critics worrying it could lead to a flurry of DUI arrests.

"It's just a law enforcement sting in plain sight," said Seattle marijuana lawyer Jeffrey Steinborn. He said the federal government, which has its own anti-pot laws, could sweep away most of I-502, leaving the new drugged driving standard.

Almost lost in this back-and-forth are critics of legalizing pot. While they don't have their own ad campaign, they are speaking out.

On Monday, nine former heads of the Drug Enforcement Administration urged U.S. Attorney General Eric Holder to denounce the marijuana measures in Washington, Oregon and Colorado.

Peter Bensinger, who held the top federal drug post from 1972 to 1982, dismissed the idea of regulating – not banning – the drug.

"Marijuana is not healthy," he said, "and marijuana creates major, major safety problems, in the workplace, on highways and with young people and their brain development."

Bensinger argued that if I-502 passes, drug gangs will focus even more intently on selling marijuana to youths. He also cited a study that found youths who began to smoke pot regularly at 13 wound up losing an average of eight IQ points by the time they were 38.

Kevin Sabet, a drug policy expert at the University of Florida and former Obama administration official, said legalization would inevitably make marijuana more acceptable and lead to greater use by youths.

Look at the prevalence of alcohol abuse and tobacco addiction, he added, which doesn't "provide us with any comfort about regulating marijuana."

Sabet is also convinced federal authorities will not allow I-502 to stand if it passes.

Holcomb said she hopes she can persuade the feds that the initiative "could help with federal efforts to combat the large criminal organizations."

Steves, meanwhile, says he thinks legalization could help turn marijuana into a rather boring diversion that most people will avoid – like they do in the Netherlands and other countries where marijuana use is tolerated.

"It's almost ridiculous what a big thing it is," he said. "I have friends in Europe who say it's not that big of a deal. They legalize it and use doesn't go up."

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