The gun control compromise fashioned by Sens. Joe Manchin (D-W.Va.) and Pat Toomey (R-Pa.) was defeated in the Senate on Wednesday in the first major vote of a marathon session.

The amendment, which would have required background checks on all commercial sales of guns, got the support of 54 members and was opposed by 46. It needed 60 votes to move forward.

The bill, which was expected to come up short, lost the support of four Democrats on Wednesday: Sens. Max Baucus (Mont.), Mark Begich (Alaska), Heidi Heitkamp (N.D.) and Mark Pryor (Ark.). All four but Heitkamp face difficult reelections in 2014, and all come from rural states with strong gun cultures. Senate Majority Leader Harry Reid (D-Nev.) voted against the amendment for procedural reasons.

Four Republicans voted in favor of the bill: Sens. Susan Collins (Maine), Mark Kirk (Ill.), John McCain (Ariz.) and Toomey.

After the vote, Toomey expressed regret but said that it was time to move on.

“I did what I thought was the right thing for our country. I sought out a compromise position that I thought could move the ball forward on an important matter of public safety,” he said in a statement, adding later:  “We have a lot of other very important issues to deal with such as getting the economy back on track, dealing with the debt ceiling and creating more jobs for Pennsylvanians.”

The raw emotion of the defeat played out in the Senate gallery just after Vice President Biden read the vote count.

“Shame on you!” at least two women were heard shouting.

As they were escorted from the Capitol, Patricia Maisch and Lori Haas said they had shouted in anger. Maisch knocked a large ammunition magazine out of the hands of Jared Loughner in Jan. 2011 after he shot former Rep. Gabrielle Giffords (D-Ariz.) and other bystanders.

“They are an embarrassment to this country, that they don’t have any compassion or care for people who have been taken brutally from their families,” Maisch said as officers attempted to remove her from the building. “I hate them,” she said of the senators.

“We’re sick and tired of the death in this country and these legislators stand up there and think it’s a bunch of numbers,” said Haas, whose daughter, Emily, was wounded in the April 2007 shooting at Virginia Tech.

“It’s a shame, it’s appalling, it’s disgusting,” she added.

The Senate will hold votes on eight more amendments Wednesday afternoon.

Ed O'Keefe contributed to this report.