Despite an impassioned push by President Barack Obama and an emotional lobbying effort by the families of mass shooting victims, proponents of a compromise measure to expand gun background checks on Wednesday fell six votes short of passage in the Senate.
The vote on the amendment was 54 to 46. Sixty votes were needed for the amendment to be adopted.
The deal was the result of a deal struck between Republican Pat Toomey of Pennsylvania and Democrat Joe Manchin of West Virginia.
As the bill was defeated, a voice in the Senate gallery could be heard yelling "Shame on you!"
The Manchin-Toomey amendment would have extended existing background check rules to gun sales made online and at gun shows. It was vehemently opposed by the National Rifle Association, who said it infringed on the rights of gun owners.