OLYMPIA — After struggling to sway both state and federal lawmakers, proponents of expanding background checks for gun sales are now exploring whether they will have more success by taking the issue directly to voters.

While advocates generally prefer that new gun laws be passed through the legislative process, especially at the national level, they are also concerned about how much sway the National Rifle Association has with lawmakers.

Washington Rep. Jamie Pedersen, a Democrat who had sponsored unsuccessful legislation on background checks at the state level, said a winning ballot initiative would make a statement with broad implications.

“It’s more powerful if the voters do it — as opposed to our doing it,” Pedersen said. “And it would make it easier for the Legislature to do even more.”

On Monday, proponents of universal background checks in Washington will announce their plan to launch a statewide initiative campaign that would require the collection of some 300,000 signatures, according to a person involved in the initiative planning who spoke on condition of anonymity so as not to pre-empt the official announcement.

The Washington Alliance for Gun Responsibility has scheduled a fundraiser in Seattle at the end of next month and hopes to have a campaign budget in the millions of dollars.

Ballot measures may be an option elsewhere, too. Hildy Saizow, president of Arizonans for Gun Safety, said an initiative is one of the things the group will be considering as it reconsiders strategies. An organizer in Oregon was focused on the Legislature for now but wouldn’t rule out a ballot measure in the future if lawmakers fail to pass a proposed bill there.

While advocates have had recent success on background checks in places like Connecticut and Colorado, they’ve been thwarted in some other states and in Congress. The U.S. Senate rejected a plan to expand background checks earlier this month, although lawmakers in the chamber are still working to gather additional votes.

Brian Malte, director of mobilization at the national nonprofit lobbying group Brady Campaign to Prevent Gun Violence, said passage through Congress is the ideal in order to have a national solution and so that states with strong gun laws aren’t undermined by nearby states with weaker standards. He noted that initiative campaigns are costly endeavors that can drain important, limited resources.

Still, Malte said, the ballot measures are an option to consider.

“At some point, certainly decisions need to be made about what the right time is to say we take it to the people,” Malte said.

Brian Judy, a lobbyist who represents the NRA in Washington state, did not return calls seeking comment about the new initiative. He has previously said the NRA would likely oppose such an effort, arguing that the recently proposed laws on background checks would largely impact law-abiding citizens instead of the intended targets such as criminals and the mentally ill.

Gun measures have had mixed results at the ballot. More than 70 percent of Washington state voters rejected a 1997 initiative campaign that would have required handgun owners to pass a safety course. After the Columbine High School massacre in 1999, voters in Colorado and Oregon approved ballot measures the next year to require background checks for buying weapons at gun shows.

Following another massacre in Colorado earlier this year, state lawmakers approved a bill to expand background checks to private transactions and online purchases. A similar expansion plan in Oregon is stalled in the state Senate.

Some states don’t see initiatives as a viable option right now. In Missouri, state Rep. Stacey Newman has been pushing for background checks with little success. While she spoke positively about the idea of a ballot initiative, she said there’s no serious consideration of it because of the cost and coordination required just to get it on the ballot. Instead, the supporters of background checks in the state are simply working to prevent NRA-supported legislation from passing the state’s General Assembly.

“We’re continually on defense,” she said.

Gun buyers currently must undergo a background check when they purchase a weapon from a federally licensed firearms dealer but can avoid checks in most states by using private purchases, such as at gun shows.

Washington state advocates believe polls show the public is sufficiently on the side of expanding background checks further. An independent Elway Poll conducted two months ago found that 79 percent of registered voters in Washington state supported background checks on all gun sales, including private transactions.

That wasn’t enough to shepherd the bill through the Legislature. Even in the state House, which is controlled by Democrats, supporters fell short after an NRA campaign put pressure on some lawmakers. Pedersen had offered concessions through the process, including the option of sending the measure out for a public vote and exemptions for people who already have concealed pistol licenses or law enforcement credentials.

Pedersen said he was working with the initiative organizers on language for the proposal, and he said the Legislature would first have another chance to adopt the measure early next year. If it fails among lawmakers again, the proposal would then automatically go to the ballot, where Pedersen said he welcomed a campaign competing against groups like the NRA.

“I’m not afraid of it at all,” Pedersen said. “The public is really with us. It’s the right policy. I think it can be useful for further progress.”