Rohani has many tigers by the tail. The IRGC: saw its power grow huge under the sanctions regime, its smuggling operations corrupted it, turning it into a parallel state: Iran’s own Hezbollah. Now it is fighting a hugely unpopular war in Syria that has largely destroyed its standing with everyone including the Iranian electorate. Does it want rapprochement with the west? It only stands to lose. The IRGC deeply desires nukes, its the only way to secure its power, wealth and agenda indefinitely (much like the ISI in Pakistan).
The religious: are divided but for the most part have started to follow the Ayatollahs in Najaf, Iraq, especially the Iranian born Grand Ayatollah Sistani who is now the leading cleric in Shi’a Islam. Qom also is deeply divided, much of it is tainted by Khamenei’s political machinations. Sistani and the words of the late Montazeri resonate far more profoundly than that of the religiously lightweight Khamenei.
The electorate: gave Rohani a massive mandate. He secured more than 50% in the first round of voting, besting 6 other candidates. The runner up secured less than 17%. Iranians expect much from Rohani, deliverance from political Islam, the Basij and the IRGC certainly is the top unmentioned theme. Rohani needs leverage, a solid political deal with the west would be very popular and could unhinge the power of the Khamenei group.
The West: wants to believe but too many may not want to lift sanctions while the IRGC maintains its independence. Its a chicken and egg quandary.
Israel: continues to issue forth rhetoric that is music to the ears of the IRGC. Rohani has little alternative but to respond in kind in order to remain in some good graces with hardliners.
Lots of tigers by the tail! The threat of force to silence political opponents remains almost as present as it was in 2009. The potential for millions of people taking to the streets in support of their President also is considerable.
I think the biggest tiger by far is the Iranian electorate. Rafsanjani is deeply committed to making this presidency a success, it is his last chance to put his mark on events. Nobody wants a repeat of 2009 or worse. I think Rohani will prevail but will need more than a token deal to bring home. Iranians are hungering for restoring international relations and are more ready for a liberal democracy than any other people in the wide region (except perhaps the Turks).