As we've noted before, the math remains very tough for the gun bill, with basically all remaining undecided senators needing to vote for it, in addition to getting Sen. Frank Lautenberg (D-N.J.), who has been ill in recent weeks and unable to travel, to the Senate chamber.

Amendments to the gun bill require 60 votes, meaning Democrats needed to pick off a number of Republicans in order to pass it. So far, only three -- including Toomey -- have signed on, and several Democrats have wavered as well.