Washington voters decisively backed expanded background checks for guns, a victory for advocates of stricter gun laws who say they will use the momentum from to pursue similar measures in other states.

With the passage of Initiative 594, Washington joins six other states and the District of Columbia with laws that require universal background checks for all sales and transfers of firearms, though it is the first to pass such a law through a citizen-driven initiative on the ballot.

Supporters say Washington will be a model for other states. Signature-gathering for a similar measure in Nevada is wrapping up, and supporters say Arizona and Maine are among the states being considered for initiative campaigns.

Washington voters rejected a competing measure Tuesday that would have prevented expansion beyond the federal standard.