"Okay I'll play. What specific actions has our esteemed Constitutional expert lawyer, Levin, put forth to offset the Constitutional requirement for 2/3 vote majorities to override vetos?"
Note, please, Mark was talking about the Iran deal.
(1) McConnell could have prevented the Corker bill which changed the nature of the debate from a treaty requiring 2/3s approval to an executive agreement requiring only 60 votes for approval thus allowing the Dems to more easily block disapproval...which they did.
(2) He could have pulled a Reid and changed the rules, just like Dirty Harry did, and require a simple majority to cut off debate and any chance at filibuster. He didn't and the reason is obvious: despite how bad the agreement is, and how much the public detest it (remember them?), McConnell is in Obama's pocket and he wanted this agreement to be adopted.