Those conservatives still attempting to defend the letter that was sent by 47 GOP senators to the leadership of Iran are citing the Constitution's "advise and consent" clause as the legal underpinning for that decision.

However, if you read the Constitution closely, I believe you'll find that the person whom senators are supposed to offer advice and consent is the president of the United States. Offering advice and consent to leaders of an antagonistic foreign power -- especially advice that directly undermines the authority of the duly elected American president -- is quite a different matter.

We're still far from certain that a deal can be reached, but if it happens, it will be a deal between Iran and the six major nations that have imposed crippling economic sanctions on Iran to force it to the table, and that have negotiated with Iran for well over a year.

That's a critically important point. If a deal is reached, each of those six countries -- the United States, France, Germany, Britain, China and Russia -- will play roles in enforcing it and will have to take steps to implement it, such as gradually relaxing sanctions as a reward for each step that Iran takes on its end.

In addition, constant inspections will be needed to ensure that Iran is abiding by the agreement. Those inspections would be carried out by the well-respected International Atomic Energy Agency, which has played a leading role in exposing Iran's nuclear activities and demanding accountability. Because the IAEA is a United Nations agency, the approval of the United Nations Security Council will be needed to allow it to play that role.

In short, this would not be a deal between Iran and the United States. It would be a deal between Iran and the larger international community. The United States, on its own, never could have brought sufficient pressure on Iran to force it to negotiate. And the United States, on its own, could not ensure that Iran will abide by an agreement, should one be reached.

In that letter, Republicans correctly pointed out that a future president could walk away from any deal with Iran at any moment, since that deal will not be formalized in a nation-to-nation treaty but instead will be carried out by international agreement. It's also true that "playing well with others" is not a virtue that Republicans in general seem to value, either domestically or internationally. If you've watched their antics in Washington, they can't even get along among themselves.

But if a future president does choose to unilaterally walk away from the agreement, the onus of breaching the agreed-upon deal would be on the United States, not on Iran. We would be the "rogue nation," not Iran. Likewise, if the United States, not Iran, is seen by the rest of the world as the party that sabotages a potential deal, the willingness of our partners to cooperate in continuing and even tightening sanctions will simply evaporate. With their ham-handed letter, those 47 GOP senators made it much easier to cast the United States in that damaging role.

This is not simple stuff, and the excruciatingly important details of the nuclear inspection regimen are much more complex still. Negotiating such a deal among multiple partners with multiple viewpoints and interests takes persistence, diligence, patience and a seriousness of purpose.

And as conservative columnist Michael Gerson notes in the Washington Post, those attributes are not much in evidence among those who drafted and signed the letter to Iran. In fact, he concluded, "In timing, tone and substance, it raises questions about the Republican majority's capacity to govern":

This was a foreign policy maneuver, in the middle of a high-stakes negotiation, with all the gravity and deliberation of a blog posting."

I disagree with part of that -- a typical blog post takes a lot more work and thought than that put into the letter.

The Republican Party's other recent foray into foreign policy appears to be turning out about as well as its letter to the ayatollahs. The rapturous, swooning embrace that it gave Israeli Prime Minister Benjamin Netanyahu on his visit to chew out President Obama simply hasn't had the impact on Israeli voters that the GOP and Netanyahu had expected. Quite the contrary. Once considered a shoo-in for re-election, Netanyahu now trails in recent polling, and operatives of his Likud Party are already blaming Netanyahu's antics for their party's dimming prospects.

Here in the United States, Republicans have tried to pretend that disagreement with Netanyahu on Iran and other issues betrayed a lack of commitment to Israel's security. That's the essence of Bibi's pitch to Israeli voters as well, and in these last few days, he's pushing it with the desperation of a salesman who knows that he's just not making his numbers. Israel's "security is at great risk because there is a real danger that we could lose this election," he said this week, warning that if he loses, "You will get prime ministers who completely prostrate themselves to any pressure."

Even his fellow Israelis are getting the Neville Chamberlain treatment.

Given the complexities of the Israeli parliamentary system, it is still possible for Netanyahu to draw fewer votes than his competitors yet still survive as prime minister. But it's already clear that a lot of Israelis are deeply uncomfortable with leaders who undercut their American allies for partisan purposes, and who believe that bluster and posturing are adequate substitutes for statesmanship.

In that, we can agree.