Despite a massive push from the White House and families of the Newtown shooting victims, the U.S. Senate rejected a proposal Wednesday afternoon that would have mandated universal background checks for gun buyers and banned certain assault rifles modeled after military weapons.

Senators struck down the bipartisan amendment, proposed by Republican Pat Toomey of Pennsylvania and Democrat Joe Manchin of West Virginia, by a vote of 54–46, short of the 60 votes required to overcome a Republican filibuster. Four months after 26 students and teachers were gunned down at Sandy Hook Elementary School, the Senate’s inability to pass the background check proposal — a measure polls have found 90 percent of Americans’ support — signals the slim chances of any gun legislation moving through Congress this year.

“Today was heartbreaking — one of the saddest and most shocking days of my life in public service,” Connecticut Sen. Richard Blumenthal LAW ’73 told the News following the vote. “The hardest part of today was deciding how to explain to families that a 90 percent majority of American people and 54 senators could vote for a measure and yet have it fail, when it would save lives like the ones that were lost on Dec. 14. That is beyond shocking and shameful for America.”

Senators who opposed expanding the background check system argued that such a measure would be ineffective in preventing criminals from procuring guns. They said it may also lead to the creation of a federal registry of gun owners, which is currently prohibited under federal laws.

“Criminals do not submit to background checks,” said Sen. Charles Grassley, an Iowa Democrat who voted against adopting the amendment.

Four Republicans voted in favor of the amendment, and four Democrats opposed it. It is still unclear how the Democratic-controlled Senate will proceed after this defeat. Connecticut Sen. Chris Murphy told the News that Senate leadership may pursue other avenues to reintroduce a background check proposal, including proposing a watered-down amendment or tacking the proposal onto future legislation.

Blumenthal and Murphy have been lobbying the Senate for the past several months to pass the background checks amendment. More recently, family members of Newtown victims have joined the national debate, traveling to Washington to lobby Congress and appearing alongside President Barack Obama in Hartford earlier this month.

Steven Barton, a Connecticut resident who was wounded in the Aurora movie theater shooting last July, traveled with the Connecticut delegation to persuade senators to adopt what he considered were “common-sense” gun-control measures. In a press call held soon after the vote, he expressed frustration at the insensitivity he experienced from senators unwilling to support his position.

“I can’t tell you how discouraging it is and how insulting it is to sit across from a senator and have them tell you that a background check is a bridge too far,” he said. “While this is a setback, we’re not leaving — we’re not going anywhere.”

Murphy said that since a majority of senators had voted in favor of background checks, he will move to actively fight the filibuster rule.

“This vote has turned me from a proponent [of abolishing the filibuster] into a revolutionary,” Murphy said. “There’s never been a bigger gap between the American public and a Senate vote.”

Also on Wednesday, a ban on assault weapons fell 40–60, and a ban on high-capacity magazines was rejected, with 46 senators voting in favor and 54 against.