The actions of the newly-inaugurated Iranian president will decide whether the optimism about his election is justified.
Rouhani has to justify his hopes for the new Iran
Despite months of speculation and outright guesswork about what the election of Hassan Rouhani will mean for Iran and for the region, his inauguration yesterday begins the era when his actions will determine whether the optimists or the pessimists will be proved right.
Both have been able to proffer plenty of material in their favour but with his presidency less than a day old, we suggest the starting point has to be one of cautious optimism.
The signals have so far generally been positive. Although no doubt triggered more by the effect of sanctions on the Iranian economy than by a sudden belief in international bonhomie, most of the statements coming from Mr Rouhani have been notably more open and conciliatory than the inflammatory rhetoric of his predecessor, Mahmoud Ahmadinejad.
This ties in with another change in the presidency. Mr Ahmadinejad's second term was characterised by the low-level antagonism with Iran's supreme leader, but Mr Rouhani is from within Ayatollah Ali Khamenei's camp. So the early signals from the new president are seen - by the optimists - as possibly indicating the views of Iran's ultimate leader.
Western-led sanctions are clearly hurting the country. Iran's hard-currency reserves and oil revenues are both falling rapidly, and that financial haemorrhaging is bringing home to the average Iranian the true cost of its popular nuclear programme. Economic matters loom larger than foreign policy successes in the minds of most citizens.
But there are also clear grounds for pessimism. If the Middle East's history teaches anything, it is that green shoots of hope more often than not wither to brown husks of disappointment. In that context there is disappointing news from Washington: for all the talk from Barack Obama at his first inauguration about extending the hand of friendship if nations like Iran would unclench their fists, Mr Rouhani's conciliatory statements have been met with a new round of sanctions by the US Congress.
Still, there is hope. In Mr Rouhani's inauguration, Iran has an opportunity to change directions and start living up to its potential as a positive force in the region. Mr Rouhani, being close to the hardliners, can perhaps temper the rampant hostility of Iran's foreign policy rhetoric. And having been endorsed by the reformists, he may have the leverage to influence opinions across the leadership.