A contentious proposal to expand background checks on Washington state gun sales failed Tuesday in the state House, where supporters said they were just a handful of votes short.

In a final effort to pick up a few extra votes, Rep. Jamie Pedersen, D-Seattle, had proposed a referendum clause that would have allowed the public to vote on the measure. He initially believed that was enough to corral the 50 votes needed to pass the bill but conceded Tuesday night that others had dropped their support.

“It was too big of a stretch for this year,” Pedersen said.

Pedersen said he was disappointed by the result. The week had included lobbying from former U.S. Rep. Gabrielle Giffords, who was wounded in a January 2011 mass shooting, and Gov. Jay Inslee.

Supporters of gun control had seen this year as the greatest chance for major changes in state law, with the public still reeling from the December massacre of children at a Connecticut elementary school. The National Rifle Association, however, led a broad campaign in the state to block the bill, with opponents of the measure saying it wouldn’t stop gun violence and arguing that it was the first step to a registry of gun owners.

Gun buyers currently must undergo a background check when they purchase a weapon from a federally licensed firearms dealer. Pedersen’s proposal, crafted in conjunction with Republican Rep. Mike Hope, would have extended background checks to cover private gun transactions.

Hope, a Seattle police officer, had expressed concern that criminals have been bypassing the current system of background checks and acquiring guns through private transactions. He said the proposal won’t stop gun violence but would make it harder for criminals to get weapons.

A similar proposal in the state Senate never received a public hearing.

Proponents of gun control had recently formed a coalition to lobby on behalf of the background checks plan. Christian Sinderman, a political consultant who aided the Washington Alliance for Gun Responsibility, said it was a stark reminder of how hard it is to get votes on the issue.

Sinderman said the group would discuss future options over the next few days to determine whether it was best to continue with a legislative strategy or to consider going directly to the ballot with an initiative.

“One thing is clear: We’re not going to give up the effort on this critical public safety issue,” Sinderman said.