That letter to Iranian leaders from 47 Republican senators could well destroy critical bipartisanship in U.S. foreign policy for years to come and treacherously undermine the bargaining power of the person constitutionally authorized to conduct American affairs abroad—the President of the United States. On top of what House Speaker John Boehner did by unilaterally inviting Israeli Prime Minister Benjamin Netanyahu to address Congress, this letter seriously points to one terrible conclusion: A formidable number of congressional Republicans hate President Obama more than they love America.

These acts go entirely beyond legitimate criticism of presidential actions abroad. They are not like a few legislators wandering in foreign lands and expressing their disagreement with their government. They surely exceed the usual congressional resolutions of disagreement with presidential policy.

What the 47 did was not a trivial matter or “a tempest in a teapot,” as Senator John McCain has described it. It could well affect possible Iranian concessions in the end game. The ayatollahs could well conclude from that letter that concessions they might have made just aren’t worth it politically, as the agreement would go nowhere anyway. They’d be taking political risks for nothing.

Beyond these negotiations, the effects on our national security may well be profound and lasting. Just look at the future implications of what these Republican senators said in their letter. They maintained, in effect, that this thing a president of the United States has been negotiating will either be thrown out by Congress or discarded by the next president, so don’t waste your time. Did the 47 even consider how future Congresses would apply such words to future presidents?

For one moment, did these senators think about how their actions could affect the ability of President Barack Obama to protect the safety of America? Did they consider how their insistence that he doesn’t matter affects his power to protect American interests and lives in the Middle East or NATO countries? These noble legislators were saying Mr. Obama doesn’t speak for Congress or the American people, and bad guys of the world, you can defy him and thus the United States however you wish.

And don’t think for a second that Democrats will forget these acts of near-treachery to a sitting president of their party when a Republican president takes the helm. Don’t expect the Democrats to be saints and models of self-restraint given the behavior of Speaker Boehner and these 47 Republicans. At some critical time, in some critical place, Democrats will exact revenge on a Republican in the White House and, alas, on U.S. national interests. At some point, the Republicans will reap what they have sown.

Seven sitting Republican senators fully realized the consequences of what their colleagues were doing and refused to sign the letter. Those with such good sense merit mentioning: Bob Corker, Lisa Murkowski, Jeff Flake, Lamar Alexander, Susan Collins, Dan Coats, and Thad Cochran. At least some senatorial Republicans put their country above partisanship, blind ideology, and hatred of the duly elected president of the United States.

Many Republican worthies who have conducted U.S. national security policy in the past and who may do so in the future know well that the agreement being negotiated with Iran by Mr. Obama is not another Munich or a sellout, as Israel’s prime ministerial hit man intoned to Congress. Putting all the baloney aside (and boy there are mountains of it this time), in the simplest terms this agreement extends the time for an Iranian nuclear breakout to a bomb and enhances our knowledge of what’s going on with nuclear programs inside Iran through greater inspections.

It’s surely not heaven, and the Iranians surely can’t be trusted, but it’s surely better than the idiotic alternatives. These would be forgoing the agreement and letting Iran simply get to a bomb quickly, as the severest critics fear they will, or going to war with Iran to delay that day.

Those who argue that Iran will be brought to its knees by enhanced economic sanctions ignore history. Look at North Korea, Pakistan, Cuba, and so forth. Look at the fact that a large majority of Iranians feel they should have peaceful nuclear energy capability. Look at the fact that all the countries partnering with the U.S. in negotiating with Iran (Britain, France, China, Russia, and Germany) back the current negotiating track, which includes a gradual lifting of economic sanctions. And stare at the reality that if we stiff our own sensible negotiating track with Tehran, then our negotiating partners will lift their own sanctions from Iran without an American “OK.”

The White House was right on the mark in saying that the only ones who rejoiced at the Republicans’ unintelligible rant were the hardliners in Tehran. They don’t want the agreement either. Have these 47 Republican senators ever wondered if they might be green-lighting those in Tehran who yearn for Iran to be a nuclear power?

The House Republicans who invited a foreign leader to Congress to attack the president of the United States, and the 47 Republican senators who undermined U.S. national security with their letter, can’t be expected to repent. Anyone who would do these things may well be beyond redemption. But Republican leaders who have effectively and nobly carried out U.S. foreign policy in the past and may do so in the future must step up now to protect America’s future.