This story has been updated.

As the Senate began voting Wednesday on nine proposed changes to a gun control bill, the centerpiece proposal on background checks quickly failed to win enough support, despite broad public backing.

Sen. Joe Manchin (D-W.Va.). Sen. Joe Manchin (D-W.Va.).

The vote on the so-called Manchin-Toomey amendment was 54 in favor, 46 against -- failing to reach the 60-vote threshold needed to move ahead. Four Republicans supported it, and four Democrats voted no.

A controversial Democratic plan to ban dozens of military-style assault weapons was also defeated by a vote of 40 to 60.

The votes were a setback for President Obama, who angrily blasted Republicans for defeating the background check compromise, saying, “The gun lobby and its allies willfully lied about the bill."

“All in all, this was a pretty shameful day for Washington,” Obama said, promising that “this effort is not over.”