Initiative 594, the ballot measure to close the “gun show loophole,” enjoys a 2-to-1 lead and surprising strength on both sides of the Cascades, according to a statewide KCTS-9 Washington Poll, set to be unveiled Wednesday night the public TV station.

A total of 57.2 percent of Puget Sound-area voters said they would definitely vote for I-594, with 11.9 percent leaning toward a Yes vote: 46.8 percent of those surveyed in Eastern Washington are solidly for the measure, with 7.7 percent leaning Yes.

The total finding for the state is 52 percent definitely voting for I-594, which would require criminal background checks for those purchasing firearms at gun shows and on line. An additional 9.1 percent lean toward supporting I-594.

“We are seeing widespread support for Initiative 594 for background checks across the state: While support is highest in the Puget Sound region which traditionally leans left, it also has majority support in Eastern Washington,” said Matt Barreto, a University of Washington political scientist.

Barreto and UW colleague Christopher Parker were principal investigators in the survey, which was done for KCTS. KCTS host Enrique Cerna will unveil full results at 8 p.m. on Wednesday.

A rival measure, Initiative 591, backed by the Gun Lobby, gets definite support from only 34.4 percent, with 7.3 percent leaning toward a Yes vote. An almost equal number oppose the measure. I-591 would block the state from enacting any gun safety measure that is not already a federal requirement.

The findings of the Washington Poll track closely with an Elway Poll released earlier this month. It found voters in favor of I-594 by a 60-31 percent margin, with I-591 support having dropped to just 39 percent.

“Initiative 591, which would stop any new background checks, we find the public more split,” said Barreto. “However, I would expect enthusiasm for 591 to wane following the Marysville shootings. Typically if initiatives are not above the 50 percent mark in polls before election day, the have a hard time winning as more undecided voters tend to vote No.”

The poll was conducted Oct. 17-24, and involved land line and cell phone interviews with 602 registered voters. It has a margin of error of plus/minus 4.0 percent.

The full results of the poll, including favorable/unfavorable ratings for state and national political figures, will be posted Wednesday on the KCTS website: www.kcts9.org

The National Rifle Association has enjoyed success in past Washington elections, setting out to make examples of candidates and causes.

In 1994, it imported NRA President Charlton Heston to campaign against U.S. House Speaker Tom Foley. Foley was a longtime NRA ally, but supported a ban on military-style assault rifles after a mass shooting at Spokane’s Fairchild Air Force Base.

A free-spending NRA campaign, in 1997, defeated an initiative to require trigger locks on stored weapons and a firearms safety course for new gun purchasers.

The advantage in 2014 has belonged to the proponents, a campaign begun when Seattle faith leaders met after the Newtown, Conn., shootings, and has gradually grown into a $10 million statewide effort.

“The spate of unconscionable school shootings across the country, and now here in Marysville, has left voters ready to take responsible action on gun issues,” Barreto said. “We saw the same thing in 2012-2013 following the Newtown killings. There was widespread public support for background checks, however, the U.S. Congress failed to get anything done.”

“The difference here is that the power is in the hands of the voters themselves because this is an initiative in which voters can bypass the Legislature and get things done themselves.”

Opposition to I-594 is both more visible and stronger outside the Puget Sound area.

Just 19 percent of Puget Sound area voters say they will definitely vote against the gun measure, with about 3 percent leaning toward a No vote.

The No figures in Eastern Washington jump to 35.1 percent in the definite No camp, with another 5 percent leaning against. Elsewhere in Western Washington, the No percentage is 40.9 percent, with 33.1 percent saying they are certain to vote No.

The Washington Poll has a record of accuracy. It has been particularly strong spotting tiny leads in close races, and detecting trends on controversial statewide ballot measures.