Not being stupid, Governor Walker surely lied when he said this:
“I will terminate that deal. I will put in place crippling economic sanctions on Iran, and I will convince our allies to do the same.”
There isn't any chance that Walker doesn't know that the current sanctions only existed for the possibility of that deal, and have no chance of holding if it is "terminated". He also knows that it isn't possible for the United States on its own to impose "crippling economic sanctions". That would require a broad coalition.
If a Republican president kills that deal, war with Iran is inevitable. The only remaining option will be military action, and bombing Iran's nuclear facilities will be considered an act of war and they will retaliate, most likely against Israel, and it will escalate from there. The U.S. will not remain on the sidelines if Israel goes to war with Iran.
Prime Minister Netanyahu lied when he said this:
"The alternative to this deal is a better deal".
There was never the slightest chance of a deal that would satisfy Bibi, and he isn't the faintest bit interested in a deal of any kind that keeps the Iranian government intact. Bibi's strategy is to cajole and manipulate the United States into a situation where war with Iran becomes unavoidable, so that we, not Israel, will make a regime change then occupy the country forever, because permanent occupation by the U.S. is the only possible way to prevent the country from falling into the hands of Islamic extremists if the government falls.
Every Republican candidate for president is staking out a position that would ultimately lead to war with Iran. Maybe all of them don't believe they are trying to take the United States into another war, but that is in fact what they are doing, even the ones that are too dumb to realize it, and all of them will lie their asses off to defend their position.
This is what is at stake in 2016. It's great fun to mock the clown car, but this is no joke. They are all clamoring to be the next war president, and you can't trust a word that comes out of their mouths.