The Senate rejected an effort to expand background checks on gun purchases proposed by Sen. Pat Toomey, R-Pa., on Wednesday.
Co-authored with Sen. Joe Manchin, D-W.Va., the Public Safety And Second Amendment Rights Protection Act fell six votes shy of the needed 60-vote threshold.
The bill had been hailed by some as a "common sense" measure to expand background checks for firearms purchases at gun shows and over the Internet but had drawn criticism of some conservatives and particularly of members of tea party groups.
About 50 tea party members protested outside Toomey's Johnstown office on Tuesday about the gun legislation.
"I did what I thought was right for our country," Toomey said in a statement following the vote. "I sought out a compromise position that I thought could move the ball forward on an important matter of public safety.
"My only regret is that our amendment did not pass."
The Manchin-Toomey amendment failed in a 54-46 vote.
Speaking from the Rose Garden and flanked by families of victims of the Tucson, Ariz., and Newtown, Conn., shootings, President Barack Obama said Senate Republicans had no excuse for failing to pass the amendment.
"Instead of supporting this compromise, the gun lobby and its allies willfully lied about the bill," Obama said.
Only four Republican senators, including Toomey and Sen. John McCain of Arizona, voted for the amendment.
Obama echoed Toomey's description of the proposed amendment's "common sense" measures.
"There are no coherent arguments for why we didn't do this. It came down to politics," Obama said.
Sen. Bob Casey, D-Pa., voted in favor of the legislation.
Senate Democrats who voted against the amendment also were chided by Obama for "caving to the pressure."
"Shame on you," yelled Patricia Maisch immediately following the Senate vote. Maisch prevented Tuscon shooter Jared Loughner from reloading during an assassination attempt on U.S. Rep. Gabrielle Giffords.
Maisch, as well as families of victims from the Newtown; Aurora, Colo.; and Tuscon shootings were present during the Senate vote.
Speaking with Pennsylvania reporters earlier in the day, Toomey touted support of the bill from The Citizens Committee for the Right to Keep and Bear Arms and the Pennsylvania District Attorney's Association.
But CCRKBA pulled its support of the Toomey-Manchin amendment hours before the vote on the Senate floor Wednesday afternoon.
"Our support for this measure was contingent on several key provisions, the cornerstone of which was a rights restoration provision that is not on the schedule for consideration," Alan Gottlieb, CCRKBA chairman, said in a statement. "This is not a reflection against Sen. Joe Manchin or Pat Toomey, who are staunch Second Amendment advocates, and I want to thank them for all of their efforts to include as many protections for our gun rights as possible."
In an interview on MSNBC Wednesday morning, Manchin said he was hopeful his Senate colleagues would vote in favor of the amendment.
Manchin said it was "not a heavy lift" to pass the legislation.
"I can't understand it; I really can't," Manchin said of opposition to the amendment.
The legislation was "just common sense" and designed to keep guns out of the hands of criminals and mentally unstable individuals, Toomey said.
The amendment would require background checks for all gun purchases made online or at gun shows and would establish a national commission to examine the causes of mass violence.
Speaking on the Senate floor ahead of the vote, Toomey was adamant that the bill was not designed to ban any types of firearms, limit ammunition magazine sizes or create a national firearms registry.
Hours before the amendment was voted on, Toomey told Pennsylvania reporters he had faced a constant battle against misinformation circulated about the provisions of the bill.
And Toomey reiterated he was unconcerned with any potential political backlash from the National Rifle Association.
"This is not about the NRA, and this is not about politics for me," Toomey said.
The Associated Press contributed to this article.