Judging from the reaction from the White House and its cheering section in the liberal media, the administration is convinced that the nuclear deal it struck with Iran this week is the first step toward a fundamental change in U.S. foreign policy. By agreeing to legitimize Iran’s nuclear program and loosening sanctions in exchange for cosmetic concessions from Iran that did not roll back the regime’s dramatic advances toward its ambition to get a bomb in the last five years, President Obama has finally achieved his dream of initiating a détente with the ayatollahs that he first articulated during the 2008 presidential campaign. In doing so, he seeks to change the calculus in the Middle East and swing U.S. policy away from its traditional alliances with Israel and moderate Arab states like Saudi Arabia.

The president thinks this strategy will deter Iran from getting a bomb while also utilizing the help of the mullahs to settle things in Afghanistan and Syria. While defended by his apologists as a realist take on foreign policy, this is exactly the sort of magical thinking about Iran that characterized Jimmy Carter’s disastrous engagement with the ayatollahs. While, as I wrote yesterday, the chances that Iran will keep its word and not use American weakness and gullibility to move closer to a bomb are not zero, they are not much more than that. As for changing the region, by granting Iran a second huge victory (the first being his retreat on Syria that ensured Tehran’s ally Bashar Assad would stay in power), he has set in motion a chain of events that will further destabilize the region, make a nuclear arms race inevitable and emboldened terrorist groups allied with Iran. While this does represent a profound shift in U.S. policy, it is one that will leave the U.S. weaker, less secure, and less able to influence events than it is already.

Is there anything that can be done about this? While the president is right to think that no American ally can deter him from pursuing détente with the murderous Iranian regime–as his disdain for both Israel and Saudi Arabia makes clear–there is one factor that could obstruct his misguided attempt to essentially withdraw the U.S. from the Middle East: Congress. Only Congress has the ability to keep Obama honest on Iran.

While much of the mainstream media reacted to the Iran deal with relief at an opportunity to step back from the need to confront the nuclear peril, congressional reaction was both sober and appropriately critical. Both Republicans and Democrats rightly pointed out that the agreement the president grabbed was an unsatisfactory retreat from his past promises. Does this matter? In one sense, the answer is no. Congress is powerless to prevent Obama from signing any deal he wants with Iran. His executive powers allow him to release the billions in frozen assets that are being use to bribe the Iranians to sign the piece of paper in Geneva. But the sanctions that have squeezed Iran’s economy cannot be abrogated by presidential fiat. It will take congressional approval to do that, and if Iran is allowed to keep its nuclear toys and go on enriching uranium, that won’t happen.

Thus, despite his urging, it appears that the Senate will move ahead to pass the next round of tougher sanctions on Iran that have already been passed by the House. This bill will tighten the noose on the Iranian economy and make it even more difficult for the regime to go on selling its oil. But far from a breach of faith with Iran, as the administration claimed in recent weeks, passing the new sanctions will be the only thing that can keep the president honest on the subject.

As Senate Foreign Relations Committee Chair Robert Menendez indicated yesterday, the sanctions will probably be amended to postpone their implementation until after the six-month period during which the administration claims it will be negotiating a follow-up agreement with the Iranians. That will give President Obama a chance to prove that his deal is not merely an effort to appease Iran and that he is still serious about halting their push toward a weapon. But if six months from now the Iranians have still not agreed to dismantle a single centrifuge or given up their stockpile of enriched uranium, the sanctions will not be delayed.

As most members of Congress seem to recognize, the choice here was not between war and an unsatisfactory nuclear deal. They rightly disagree with the idea that Iran is too strong to be further opposed or that it is unrealistic to suppose the West can force the regime to give up their nuclear dream. While the signal of weakness from the administration to the Iranians may have convinced them they need not fear the use of force or continued sanctions, a determined stand by Congress may be the only thing that can act as any sort of deterrent against an Iranian nuclear breakout.

The push to pass sanctions will likely be criticized as the work of the dreaded “Israel Lobby,” and we have already begun to hear calumnies of those pushing to restrain Obama’s appeasement as being merely a function of the Jewish state’s instructions. One such statement came last week from Carter administration National Security Adviser Zbigniew Brzezinski who tweeted, “Obama/Kerry = best policy team since Bush I/Jim Baker. Congress is finally becoming embarrassed by Netanyahu’s efforts to dictate US policy.” If “best policy team” means most hostile to Israel, he’s probably right. But the key here is the attempt to brand members of Congress who won’t buy into Iran détente as being, in New York Times columnist Thomas Friedman’s phrase, “bought by the Jewish lobby.”

But I doubt Democrats like Menendez or Chuck Schumer or Republicans like Bob Corker or Lindsey Graham will be deterred by this kind of slander that borders on open anti-Semitism.

While Congress can’t stop the president from embarking on this potentially disastrous course of action toward Iran, it can make it impossible for him to further reward the ayatollahs if they continue their past policy of deceiving the West. The president may hope that once agreements are signed, the world will stop caring about Iranian nukes. But the House and the Senate should use their power of the purse to obstruct such a craven retreat from American responsibility. They are the only ones who have any hope of keeping Obama honest on Iran. And they should not be intimidated from doing so by anti-Semitic slanders.