Tear gas can stimulate the salivary glands of people hungry for regime change, even if those people belong to a different country and are thousands of miles away from the streets where the gas canisters are being fired. This may become one of the effects of protests in Tehran by money changers and bazaaris upset over the collapse of the Iranian currency. Whether the protests expand into anything politically significant is unpredictable. They may be too narrowly aimed at the lame-duck president, Mahmoud Ahmadinejad, to become a serious challenge to the regime. What is more predictable is the reaction of anti-Iran activists in the West (and Israel). An immediate reaction from those stoking the idea of a military attack on Iran has been to warn people away from the “sanctions are working” idea while nonetheless calling for still more sanctions. Don't be surprised to hear as an additional argument (despite any logical inconsistency with the first argument) that it would be a mistake to let up the pressure on Iran—regardless of what it does in negotiations over the nuclear issue—at a time when the mullahs' regime seems to be teetering and there is hope for being rid of that regime once and for all.

Resistance to any lessening of sanctions as part of a negotiated agreement with Iran on the nuclear question has, unfortunately, already been strong, even before the newest protests. That resistance has been reflected in the relatively inflexible negotiating posture to date of the United States and its partners of the P5 +1. A hope in some quarters that economic pressure will hasten the demise of the current Iranian regime no doubt is one of the causes of that resistance, even though that is not explicitly an official objective of the sanctions. The more that street protests in Tehran sustain that hope, the stronger is likely to be resistance in the United States to any sanctions relief, and the more politically difficult it will be for any American administration to strike a nuclear deal, which would require such relief.

Secretary of State Clinton, in noting the multiple reasons for Iran's economic failures, said on Wednesday, "Of course the sanctions have had an impact as well, but those could be remedied in short order if the Iranian government were willing to work with the P5+1 and the rest of the international community in a sincere manner." That is a good description of how the sanctions are supposed to be used. Sadly, it does not describe how the P5+1 have used them so far in the negotiations.

As the history of the USSR (consistent with how George Kennan envisioned it in the 1940s) illustrates, there need be no contradiction between engaging and striking deals with a regime we don't like, and seeing that regime crumble as a result of its own internal weaknesses. There is a contradiction in any attempt to use the same policy instruments (in this case sanctions) both to influence a regime's policies and to try to topple it. The inflexible application of pressure in pursuit of the toppling objective renders unusable the same sort of pressure as leverage—which requires flexibility—to elicit changes in policy. To the extent inflexible application continues to be the case with the approach toward Iran, the resulting stalemate will of course be interpreted as an indication of Iranian obduracy—whereas in fact it is an indication of confusion in the use of our own policy instruments.

Holding out hope that sustained pressure will hasten regime change in this case represents a bad bet. It means placing trust in a very uncertain process—notwithstanding the tear gas in Tehran streets—while jettisoning an important tool that if properly used would help lead to an agreement that would satisfy all legitimate concerns about nuclear proliferation as it pertains to Iran.

Even if regime-change-wishers had a better bet to make, they need to think hard about what they are wishing for. Much of what they don't like about Iran is not unique to the Islamic Republic and would continue under any imaginable successor regime. That includes the current nuclear program, which began under the shah and has broad public support. It also includes many other things, including opposition to Israeli policies in the region.

We should have learned some things in this regard from our regime-changing experience in Iraq, where the regime we have been left with is narrowly sectarian, increasingly authoritarian, and pro-Iran.