When a bipartisan proposal for expanding background checks on gun purchases comes up for a Senate vote this week—possibly as soon as Wednesday—neither Sens. Lamar Alexander nor Bob Corker will be supporting it. 

Both of Tennessee's senators, who each voted last week to not block debate on the controversial gun rights legislation from beginning, cast their votes with the caveat that they would not favor any measures they saw as infringing on the Second Amendment rights of citizens. In remarks distributed to the media this week, Alexander said the bipartisan proposal being put forward by Sens. Joe Manchin, D-W.Va., and Patrick Toomey, R-Pa., did just that. 

"This amendment would impose a background check system that is overly broad, vague and ultimately ineffective," Alexander said. "And despite the assurances of supporters, it could easily evolve into a national gun registry that would be an intrusion into the privacy and lives of the American people. On Thursday, I voted yes to start the debate because this is a debate Republicans should want. This is a debate we can win."

Although Corker's office distributed no official comment from the senator regarding his intent to vote against the amendment, The Washington Post reported Tuesday that the senator and former Chattanooga mayor is among at least nine Republicans who said Monday that they intended to vote against the deal. 

It was not clear on Tuesday whether the amendment would be able to meet a 60-vote threshold to move forward.

Both Alexander and Corker boast "A" ratings from the National Rifle Association, which has lobbied against the amendment.