US President Barack Obama's gun control drive in the wake of the Newtown massacre suffered a major setback Wednesday when the Senate voted down expanded background checks on firearms buyers.
The measure, which would have required background checks on sales at gun shows and on the Internet needed 60 votes for approval, but it fell well short, 54-46, as a handful of Democrats either facing tough re-election challenges in 2014 or from pro-gun states stood in opposition of the amendment.
The White House said Obama, who has expended considerable political capital on the issue since proposing several gun safety measures in the wake of the December carnage in Newtown, would address the gun reform effort at 2130 GMT.
"Shame on you!" yelled Patricia Maisch -- a survivor of the 2011 shooting that left six people dead and then-congresswoman Gabrielle Giffords gravely wounded -- from the visitors' gallery. She was escorted out of the chamber.
She was one of several gun violence victims or relatives of victims, including parents or siblings of children killed in the Newtown school shooting in December, on hand to witness what they hoped would be a victory for proponents of gun control.
Instead, the Senate's members confirmed they remain deeply apprehensive about instituting any legislation that could be seen as infringing on Americans' constitutional right to bear arms.
"They have no souls, they have no compassion for the experiences that people have lived through (with) gun violence, who have had a child or a loved one murdered by a gun," Maisch said.
The handwriting was on the wall by early Wednesday, as most Republicans balked at supporting the expansion of background checks. Four Democrats as well refused to get on board with the compromise legislation.
Democratic Senator Joe Manchin earlier acknowledged to NBC News that his bill would "not get the votes today."
White House sources said the president had been calling wavering senators to push for support for the background checks bill in the hours before the vote, and his spokesman Jay Carney said everyone in the White House from Obama on down was involved.
Vice President Joe Biden, who took the rare step of presiding over the Senate for the series of votes on several gun measures, was not conceding defeat in the battle for greater curbs on firearms.
"I can assure you one thing -- we are going to get this eventually. If we don't get it today, we are going to get it eventually," Biden said during a Google Plus "hangout" event with mayors.
Shortly before the vote, Republican Senator John McCain announced his backing, but knew the amendment was already doomed.
"You did the right thing," he told Manchin on the Senate floor, commending his colleague for his commitment to a politically difficult issue.
"Sooner or later, this country will take up this issue," McCain added.
Senate Majority Leader Harry Reid has allowed votes on several amendments, including one that bans assault weapons, another which restricts the size of ammunition clips, a proposal that expands concealed-carry rights for gun owners, and a measure that funds expanded mental health programs.
A Republican-drafted measure -- which "safeguards the Second Amendment" right to bear arms by expanding funding for federal gun prosecutions and offering incentives for states to provide mental health records to the federal background check database -- failed shortly after the Manchin amendment.
Polls show an overwhelming majority of Americans support closing the loophole that allows people to purchase firearms at gun shows with no background check, but the powerful gun lobby, led by the National Rifle Association, is vehemently opposed.