Ah, the Republicans; you have to hand it to them, the chutzpah they evoke, believing they now have a mandate after last year's congressional elections gave them control of the Senate as well as the House.
The latest ploy has 47 of these senate yahoos writing "An Open Letter to the Leaders of the Islamic Republic of Iran" essentially saying any deal Obama makes with the Iranian's without legislative approval, "The next president could revoke with the stroke of a pen and future Congresses could modify the terms of the agreement at any time". 
One has to read this little missive of mischievousness to appreciate the schizophrenic, diabolical nature of US policy making today.
Oh it reads innocent enough, a calm short rendering of our constitutional system i.e. "while the president negotiates international agreements, Congress plays the significant role of ratifying them. In the case of a treaty, the Senate must ratify it by a two-thirds vote". 
All true enough. But it's a not so veiled threat to the Iranian Republic couched in legal language. Here's the response to the letter by Iranian Foreign Minister Mohammad Javad Zarif, "In our view, this letter has no legal value and is mostly a propaganda ploy. It is very interesting that while negotiations are still in progress and while no agreement has been reached, some political pressure groups are so afraid even of the prospect of an agreement that they resort to unconventional methods, unprecedented in diplomatic history."
Anyway, the whole debacle with Iran is a US led sham, the crippling economic sanctions, the ruse of an Iranian nuclear device that isn't. In fact it's still retribution toward the Iranian's for overthrowing the US backed Shah of Iran in the 1979 revolution and the taking of US embassy hostages. And ever since Iran has committed the unforgivable sin of not succumbing to US hegemony.
The negotiations with Iran are supposed to be the P5+1, the five permanent members of the UN Security Council, the US, Britain, France, Russia and China plus Germany but in all likelihood any final agreement reached with Iran will ultimately be sabotaged by the US.
And it's not just the veiled threat made by the 47 in the Senate. They're really inconsequential.
It's the whole reckless nature of the neo-cons in and out of "official" Washington that has usurped US policy making taking the US on the path to endless war, hegemony and instigating regime change all over the world and it seems a war with Russia over Ukraine.
But as Churchill once said, "It's better to jaw, jaw than make war, war".
Amen to that.