“We fell short on our first effort to pass Manchin-Toomey in the Senate, but we will not be deterred by one setback,” Biden wrote. “We have an obligation to make sure that the voices of victims, not the voice of the NRA, ring the loudest in this debate.”

Biden said he was galvanized by political developments since last month’s vote. Sen. Jeff Flake’s poll numbers have collapsed since he voted against the measure – the Arizona Republican described his popularity as “just below pond scum” – and Sens. Mary Landrieu and Kay Hagan, Democrats from Louisiana and North Carolina, have seen polling bumps.

“For too long, members of Congress have been afraid to vote against the wishes of the NRA, even when the vast majority of their constituents support what the NRA opposes,” Biden said. “That fear has become such an article of faith that even in the face of evidence to the contrary, a number of senators voted against basic background checks, against a federal gun trafficking statute and against other common-sense measures because they feared a backlash.”