The nuclear talks with Iran have just begun, but already the smart money in Tehran is betting on a deal. That comes from the Tehran stock index, which on the day after the talks opened posted its largest daily rise in months and closed at a record high.

Tehran investors may be guilty of wishful thinking. My guess is they probably have it right. So far, Iran is following the script for a gradual, face-saving exit from a nuclear program that even Russia and China have signaled is too dangerous. The Iranians will bargain up to the edge of the cliff, but they don’t seem eager to jump.

The mechanics of an eventual settlement are clear enough after Saturday’s first session in Istanbul: Iran would agree to stop enriching uranium to the 20 percent level, and would halt work at an underground facility near Qom built for higher enrichment. Iran would export its stockpile of highly enriched uranium for final processing to 20 percent, for use in medical isotopes.

In the language of these talks, the Iranians could describe their actions not as concessions to the West, but as “confidence-building” measures, aimed at demonstrating the seriousness of Supreme Leader Ali Khamenei’s public pledge in February not to commit the “grave sin” of building a nuclear weapon. And the West would describe its easing of sanctions not as a climb down, but as “reciprocity.”

The basic framework was set weeks ago,in an exchange of letters between the chief negotiators. Catherine Ashton, who represents the group of permanent U.N. security council members and Germany, proposed a “confidence-building exercise aimed at facilitating a constructive dialogue on the basis of reciprocity and a step-by-step approach.” The Iranian negotiator, Saeed Jalili, responded that because the West was willing to recognize Iran’s right to peaceful nuclear energy, “our talks for cooperation based on step-by-step principles and reciprocity on Iran’s nuclear issue could be commenced.” Jalili’s status as personal representative of the supreme leader was important, too.

“Step-by-step” and “reciprocity” are the guideposts for this exercise.

Israeli Prime Minister Benjamin Netanyahu played his expected role in this choreography, criticizing the negotiators for agreeing to another round of talks on May 23 in Baghdad without getting concessions in return. “My initial impression is that Iran has been given a freebie,” Netanyahu said. “It has got five weeks to continue enrichment without any limitation, any inhibition.” A perfect rebuff — just scornful enough to keep the Iranians (and Americans, too) worried that the Israelis might launch a military attack this summer if no real progress is made in the talks.

The Iranians seem to be preparing their public for a deal that limits enrichment, while preserving the right to enrich. In an interview Monday with the Iranian student news agency, Foreign Minister Ali Akbar Salehi explained that “making 20 percent fuel is our right,” but that “if they guarantee that they will provide us with the different levels of enriched fuel that we need, then that would be another issue.”

Jalili struck the same upbeat tone in comments printed in the Tehran Times. “We witnessed progress,” he said, explaining that the supreme leader’s religious edict renouncing nuclear weapons “created an opportunity for concrete steps toward disarmament and non-proliferation.” He said “the next talks should be based on confidence-building measures, which would build the confidence of Iranians.”

Translation: The Iranians expect to be paid, in “step-by-step” increments, as they move toward a deal. At a minimum, they will want a delay of the U.S. and European sanctions that take full effect June 28 and July 1, respectively. That timetable gives the West leverage, too — to keep the threatened sanctions in place until the Iranians have made the concessions. It’s a well-prepared negotiation, in other words, and it seems likely to succeed if each side keeps to the script and doesn’t muff its lines.

David Ignatius writes for The Washington Post.