The sweeping victory of reformist candidates in Iran's parliamentary elections is a rare bit of good news in an otherwise gloomy Middle East. The triumph of the so-called "List of Hope" of moderate and independent MPs, who appear to have scooped up all the available 30 parliamentary constituencies in the capital city of Teheran, is a huge vote of confidence for President Hassan Rouhani's reformist agenda.

To make matters better still, a key Rouhani ally is leading the race in elections to the Assembly of Experts, an obscure but important institution that is responsible for selecting Iran's supreme religious leader; with the 76-year-old Ayatollah Ali Khamenei now ailing, the assembly may have to decide soon the country's fate for decades to come.

The reformists' progress will boost hopes in the United States that the recently concluded deal over Iran's nuclear programme could be a prelude to a broader transformation of Iran into a force for stability in the Middle East. It presages a more cooperative Iranian stance in the Syrian war, a less confrontational stance elsewhere in the region, and a lower Iranian profile in other Asian countries, where the Islamic republic was resented for championing an allegedly sectarian, pro-Shi'ite Muslim policy.

As always with Iran, however, caution is required. The newly elected reformists are not a coherent block, and hardliners in Teheran will do their best to divide them. The Iranian Parliament is not the country's top decision-making body. And, with their tentacles in every business enterprise, the all-powerful Iranian Revolutionary Guards remain a potent conservative force.

Still, the parliamentary elections will boost the government's argument that, after decades of international isolation, everything should now be devoted to the country's development. Particularly for the young Iranian generation that voted for the first time, this is a real moment of hope.