Iranian Foreign Minister Mohammad Javad Zarif arrives at the parliament in Tehran, Nov. 27, 2013. (Ebrahim Noroozi/AP)

This post is part of the “Iran and the Nuclear Deal” symposium.

On the eve of the announcement of an agreement over the Iranian nuclear program, conservative members of Iran’s parliament pointedly reminded President Hassan Rouhani and Foreign Minister Mohammad Javad Zarif that any deal would have to be ratified by parliament before becoming policy. In the days since the Lausanne agreement, some members of parliament (MPs) have kept their feet on the gas pedal in attacking and criticizing the deal and its legitimacy within domestic policy. Some MPs have been quite specific in identifying weaknesses of the deal in terms of the exact number of centrifuges Iran is allowed to maintain. Still others have lambasted the entire agreement as “unacceptable” and merely Western propaganda.

So is Iran’s parliament a major obstacle to a nuclear deal in June? Not quite. Instead of intentionally blocking any international engagement, parliament is playing the role of “public defender.” MPs are vocalizing their constituents’ concerns about the fairness of the deal, whether it will ultimately improve the economy and how Iran will be perceived in the international community.

Mohammad Ali Kadivar and Ali Honari recently argued that grass-roots participation and domestic politics were crucial in getting this deal off the ground. Iran’s parliament represents another critical domestic political factor – and potentially a blocking one in the negotiation endgame. Iran’s parliament, as my research has shown in other contexts, plays a more important role than is widely understood. Aside from the presidency, parliament is the other channel through which Iran’s citizens have a voice in domestic and international politics – when it is not overruled by unelected supreme leader Ayatollah Khamenei, that is.

This matters for the Iran deal because Iran’s current parliament is a markedly conservative one. Whereas the electorate’s choice of Rouhani in the 2013 presidential election is largely seen as an endorsement of engaging the international community to resolve the nuclear issue, the parliamentary elections of 2012 gave off an entirely different message. Roughly 200 of the 290 parliamentary seats in that election were won by members of the conservative “principalists” – many of whom have close ties to Khamenei, the ultimate veto-player. This forecasted a bleak outlook for those in favor of rapprochement with the United States and Europe. Indeed, voters and politicians who fall into the pro-foreign-engagement “reformist” faction largely boycotted the election to protest the civil society fallout from the 2009 presidential election and the imprisonment of members of political opposition groups.

This conservative parliament has not thus far acted to torpedo the nuclear talks, however. In spite of parliament’s conservative swing, MPs confirmed Rouhani’s appointment of Zarif – sometimes referred to as Washington’s favorite Iranian – as foreign minister in August 2013. Nor did parliament block the president’s decision in September 2013 to shift negotiating authority from the Supreme National Security Council to the Ministry of Foreign Affairs, thereby making Zarif the top negotiator. Moreover, in early 2015, Zarif’s pro-engagement policy was initially approved by parliament. After a grueling parliamentary session allowing Zarif to advocate and to seek approval for his negotiating strategy and concessions, Iran’s MPs voted 125 to 86 in favor of his plan, with 79 abstentions.

The overwhelming majority of conservative members still makes parliament a potentially major obstacle to a nuclear deal. The months leading up to the Lausanne negotiations saw countless bombastic speeches by conservative MPs and attempts to stop the negotiations before the March deadline set by Zarif and the P5+1 negotiating team. In particular, the anti-reformist Resistance Front (Jebhe-ye Paydari) faction, led by Ayatollah Mesbah-Yazdi, took every opportunity to dismantle and discredit negotiations. In February 2015, 173 MPs voted in favor of a motion supported by the Resistance Front that would have forced the government to cancel the November 2013 Geneva “interim deal” and resume all previous enrichment activity. No damage was done to the negotiating process, however, as the motion failed to become law in subsequent sessions. Again in March, days before the negotiating team was set to meet again in Lausanne, 260 MPs issued a statement that any deal not including the full removal of sanctions and closure of the nuclear issue at the U.N. Security Council would be “null and void.” The MPs added that the country should “resume enriching uranium to the level needed in case the possible agreement is violated by the other side.”

Despite these outbursts, the majority of MPs are satisfied with the deal (notwithstanding a few amendments). Yes, the Resistance Front remains, well, resistant to the deal. But what has become an increasing trend since 2012 is the fractionalization of the conservative camp into several moderate-leaning factions, especially when it comes to the nuclear issue. These groups, notably Speaker Ali Larijani’s United Front (Jebhe-ye Muttahid-e Usulgarayan) and “moderate principalists” such as former IRGC commander Mohsen Rezaie (himself not a member of parliament), have praised the nuclear negotiating team and its outcome.

This stance roughly accords with Iranian public opinion, as best we can determine it through surveys. A survey of Iranian voters conducted in the summer by the Center for International and Security Studies at the University of Maryland and the University of Tehran Center for Public Opinion Research (UTCPOR) shows that while nearly all respondents support the negotiations, about 49 percent support restrictions on uranium stockpiles and only 24 percent would be willing to concede dismantling of centrifuges. A more recent UTCPOR survey from October 2014 found that, again despite nearly unanimous support for a deal, only 18 percent of respondents would agree to any deal that would “roll back” Iran’s nuclear achievements. And when it comes to the “rewards” of a deal, many remain skeptical: nearly 75 percent did not believe that the United States would lift sanctions following any nuclear deal.

Given the complexity of voters’ preferences over the nuclear deal, it is not unexpected that MPs continue to pressure Rouhani, Zarif and the nuclear negotiating team. Beyond representing their constituents, the role of MPs in these negotiations, however indirect, is also about saving face. This helps to explain the reciprocal provocations in the days since the deal. For example, the United States published a factsheet on Iran after the deal; MPs pressured Zarif to respond with a factsheet of their own. Europe wanted to add new sanctions; MPs held a closed session to ensure the deal includes a complete removal of sanctions (a concern echoed by Rouhani and Khamenei).

This should not be a surprise. As I have pointed out in my own research on Iran’s parliament, Iranian MPs are held highly accountable to their voters despite operating within a political system of electoral authoritarianism. They face an incredibly uphill challenge in re-election every four years, with only 30 percent of incumbents able to maintain their seats (compare that to over 90 percent in the U.S. House of Representatives). It is this same cautiously optimistic yet skeptical electorate that MPs must appeal to in the February 2016 parliamentary elections. With that in mind, it’s not surprising to hear MPs on the pulpit sometimes denouncing and other times praising Zarif’s diplomatic achievement. This electoral incentive may help to explain why the parliament’s behavior so closely tracks public opinion – in contrast to the United States, one might add, where U.S. voters overwhelmingly favor a nuclear deal with Iran but their representatives have quite vocally denounced it. As Shervin Malekzadeh recently suggested, this is one of the “great ironies” to come out of the negotiating process.

On the whole, there is broad public support for the deal within Iran. The foreign minister’s compromises in Lausanne are backed not only by the Iranian people but by their legislative representatives as well. If voters maintain their support for a “fair” deal between now and June, it won’t be parliament that blocks it. And for those MPs that continue to criticize the negotiations – and in doing so condemn Rouhani’s (and implicitly Khamenei’s) foreign policy – it will be interesting to see if they keep their seats come February.

Paasha Mahdavi is a PhD candidate in political science at UCLA and starting August 2015 will be an assistant professor at the McCourt School of Public Policy at Georgetown University. You can follow him on twitter @paashamahdavi.