The resounding win by Hassan Rouhani, the only relative moderate in this year’s Iranian presidential race, was as dramatic to world powers as it was encouraging to millions of Iranians who waited for the results last Saturday.

Rouhani, who is a cleric by training and was his country’s chief nuclear negotiator between 2003 and 2005, was not expected to win the election. Nor was he seen as a great challenger to Iran’s conservatives, an establishment that forms the nucleus of Supreme Leader Ayatollah Ali Khamenei’s support base.

Despite the doubts and his status as a wildcard during the campaign, Rouhani’s victory made clear that many Iranians had become disillusioned with the conservatism of his predecessor Mahmoud Ahmadinejad, one that has had detrimental effects on the Iranian economy and its foreign relations.

Rouhani also managed to pull of a feat that no presidential candidate in Iran has for a long time: win the vote without a runoff election.

In Europe and the United States, Rouhani’s victory will only be seen as an historic development if he opens up Iran’s nuclear program to inspectors and slows down the country’s uranium enrichment efforts. President Barack Obama, Secretary of State John Kerry and British foreign secretary William Hague all gave public statements to that effect. The United States and its United Nations Security Council partners plus Germany, who have tried to dissuade Iran from developing a nuclear weapons capability, will be waiting to see if President Rouhani follows through on his pledge to improve Iran’s relations with the rest of the world.

For the P5+1, the fact that the only Iranian moderate in the election embarrassed the favorites of Ayatollah Ali Khamenei and the Iranian Revolutionary Guard is in itself a breath of fresh air. But hoping that the next Iranian government will be more pliable in nuclear negotiations will only go so far.

Rouhani may be a more respectable and worldly figure than Ahmadinejad but he will not simply bow to the West’s demands without something substantial in return. Rouhani said as much during his first press conference on Monday, “The next government will not give up the legitimate rights of the country,” he insisted.

In Iran’s political system, the president is not the sole arbiter of foreign and security policy. That job is left to the supreme leader who must sign off on any deal before a policy shift can be implemented. Rouhani’s tenure as president will be no different. On the nuclear front, Khamenei and the Revolutionary Guards will decide whether Iran’s nuclear program is expand, continued as is or capped at a specific level

The president of Iran does, however, have the power of perception. If Rouhani is able to extract some major concessions from the P5+1 in negotiations, Khamenei may feel comfortable enough to put his stamp of approval on a deal.

With Ahmadinejad out and Rouhani set to take over his job, the West may have the best opportunity in years to find some sort of resolution to the Iranian nuclear crisis. At the very least, the tension can be dialed down to an acceptable level. Yet for Rouhani to sell any deal to the supreme leader, the international community must change its approach and offer Iran’s next president some sanctions relief to persuade the conservative establishment that there’s a point in talking at all.