[morphing libertarian]

What is the source of the 2/3 requirement to defeat a treaty in the senate?

[Democrat_media]

All the Senators voted 99-1 for the Corker bill that made Obama’s Iran deal unstoppable. Senator Cotton was the only sane one voting against the Corker bill.

http://www.americanthinker.com/blog/2015/07/forget_obamarepublicans_made_the_iran_nukes_deal_possible.html

Normally Obama would need 2/3ds approval in the Senate to pass this Iran deal but they decided to lower that to 1/3 much lower . So this corker bill is voting yes to the Iran deal. this is similar to what the Senators did with TPA giving fast track power to Obama on Obama trade.