OLYMPIA — Washington voters on Tuesday approved a plan to privatize liquor sales and dismantle controls that have been in place since Prohibition, siding with retailing giant Costco in the costliest initiative campaign in state history. Unofficial results Tuesday night showed the measure with 60 percent support in early returns. Costco Wholesale Corp. had committed $22 million to supporting the measure — $6 for every registered voter — as executives portrayed the Issaquah-based company as a crusader for consumers and said that it could take years to make up the investment in the initiative. The company also harnessed support from restaurants, groceries and other retailers.“We are very grateful to all of our coalition partners across the state,” said Joel Benoliel, senior vice president and chief legal officer at Costco. “The voters overwhelmingly demonstrated that facts trump scare tactics.” Wholesalers provided much of the opposition funding, as retailers will now be able to bypass them and buy product directly from producers. The new rules go into effect in June, and about 1,000 people who currently operate the state’s system will lose their jobs. Costco had backed another privatization measure that failed last year with 47 percent of the vote. Acknowledging that the 2010 proposal wasn’t ideal, supporters returned this year with a plan that includes more revenue for state and local governments, as well as stricter controls on which stores can sell liquor.