Secretary of State John Kerry went to Capitol Hill today to testify before the Senate Armed Services Committee about the deal to restrain Iran’s nuclear program. As expected he absorbed a lot of insults and invective from Republicans who are critical of the deal. Along with Secretary of Energy Ernest Moniz and Secretary of the Treasury Jack Lew, Kerry tried to rebut the criticisms as best he could.

But you could see in Kerry’s occasionally exasperated expression something that we all ought to be willing to acknowledge: This whole debate is a charade.

There’s a reason no Republican has managed to answer President Obama’s challenge to articulate an alternative that would be preferable to what the six-party negotiations produced, and it isn’t because this deal is perfect or couldn’t have been better. It’s that from where Republicans sit, any deal negotiated with Iran is a bad one by definition.

That’s partly because it was negotiated by the Obama administration, of course, and the GOP has gotten itself to a position where opposition to pretty much anything Barack Obama does is not just reflexive but mandatory for any elected Republican who wants to keep his job. It’s also because the sustained critique of Obama’s foreign policy that Republicans have pushed for the last six and a half years is that everything Obama does is “weak.” The word comes up again and again in Republican statements about foreign policy; ask them what they’d do differently, and in every situation their answer always revolves around being stronger. The content of this strength is rarely detailed, but when it is it usually involves more aggressive use of the military.

And it assumes that when dealing with adversaries like Iran, negotiation is weak, again by definition. Negotiation means talking to those we hate, and even offering them concessions. Successful negotiation ends with an outcome that our adversaries actually praise, when what we really want is for them to fall to their knees and surrender to our might. This is what elected Republicans believe, and more importantly, it’s what they’ve been telling their constituents for years, so it’s what those constituents demand.

So there was literally no deal this administration could have negotiated with Iran that Republicans would have agreed to. None. From their perspective, the substance of the deal never mattered. No one who has been remotely attentive to our politics in recent years could honestly deny that.

And there’s something important to understand about whether Republicans have an alternative. Yes, it’s a reasonable rhetorical point to demand that they explain what other kind of deal they’d support. But right now, they are actually proposing an alternative: that the U.S. pull out of this deal. And we need to explore what that means.

You can argue that this deal should have been different, but when it comes time to vote on whether it should go forward, members of Congress will be choosing between two options, neither of them hypothetical. A yes vote means all the parties — not only Iran and the United States, but also the United Nations, China, Russia, and the European Union — implement this deal. A no vote, in contrast, doesn’t mean that some fantasy deal will fall from the sky. It means that the U.S. walks away from this deal, and it collapses.

That also could mean that the existing sanctions regime collapses. We can keep our sanctions on Iran, but the reason sanctions have been so devastating to the country’s economy is that they haven’t just come from the U.S., but also from the United Nations, the European Union, and elsewhere. If those other sanctions were to disappear, Iran would get most of what it wanted without having to fulfill any obligations at all. And if they want to pursue a nuclear weapon, they could then go right ahead.

So now that the deal is on the table and congressional votes are on their way, what Republicans really need to explain is not what sort of deal they might have preferred. We know their answer to that question — they’ll say they would have rather had a deal where Iran gives us everything we want, and we give up nothing. But that’s irrelevant at this point. What they need to explain now is why the U.S. pulling out of this deal — and what happens afterward — will be preferable to implementing it, imperfections and all. Do they think the Iranians will come crawling back and make further concessions? Do they think the rest of the world’s powers, which support the deal they helped negotiate, will just follow us and impose new sanctions in the hope that eventually that might lead to more negotiations (which, like these, would take years) and ultimately the fantasy deal where Iran capitulates? What precisely is the chain of events Republicans think will occur if we pull out?

If they’ve given that question even a moment’s consideration, you wouldn’t know it to listen to them. But it’s what they ought to be asked now.