The Iran Accord will depend on a veto override. My thoughts going in is that Senate democrats that are up for reelection in 2016 would count the votes against and they would be allowed to vote to override veto to help with their reelection bids. I did a little research.
There are currently 27 democratic senators supporting the Accord and 4 leaning toward support. It takes 35 supporters to stop the veto override. There are 13 democratic senators still reportedly on the fence. Of those, 4 are running in 2016, and one is retiring in 2016 for a total of 5 democratic seats up for bid.
There is plenty of room to allow those running for reelection to vote against the Accord to bolster their reelections. The ones not running in 2016 will be counting on the voters forgetting about their vote in 2015. All just political show.
Neither of the NM senators are running for reelection in 16, and both are big supporters of the Accord. Don’t forget. Senator Bennet of Colorado is reportedly on the fence and up for reelection in 2016. The way Colorado seems to be going, you can place your bet that he will come down against the Accord in a show vote.