As Iranian President Hassan Rouhani begins a second term on August 5, he faces enormous political, structural and revolutionary headwinds.During his first term, Rouhani’s governing mantra of prudence and hope proved more rhetorical than real for in the end, Tehran’s crowded power arena hinders rather than facilitates real change.Three key challenges will confront the diplomat- sheikh as he sets out to make good on his campaign promises: a supreme leader who has historically neutralized the plans of presidents and prime ministers in their second terms; an energized conservative mullocracy; and an increasingly assertive Washington doubling down on Tehran’s excesses.While the modern Iranian presidency is in theory a springboard to national prominence, in practice it is essentially a political death sentence. Under the hydra-headed power structure of the Islamic Republic, it is the supreme leader – and not the president – who has veto power capable of freezing any government in its tracks. Iranians were reminded of this dynamic this summer when the supreme leader encouraged his supporters to “fire at will” any perceived enemy of the state – a not so subtle warning to the Rouhani administration.Supreme Leader Ali Khamenei’s kneecapping of Iranian politicians began in the 1980s, when Khamenei, as president, opposed Mir-Hossein Mousavi continuing as prime minister for a second term, and even lashed out publicly at Ayatollah Khomeini for pressuring him to support Mousavi. Fast-forward to 2017, Mousavi remains under house arrest after calling for protests following the rigged 2009 elections.Khamenei then thwarted the liberalization efforts of Akbar Hashemi Rafsanjani’s second term, campaigning against the Western “cultural onslaught” and creating the space for regime apparatchiks to jail journalists and attack bookstores, cinemas and theaters. Even after Rafsanjani left office, Khamenei’s one-upmanship continued. After Rafsanjani’s perceived allegiance with the protesters of the 2009 elections, Rafsanjani was stripped of his seat as head of Iran’s Assembly of Experts, his children were imprisoned and he was banned from running for the presidency in 2013.His successor, Mohammad Khatami, fared no better. Khamenei didn’t even wait for Khatami’s second term to begin flexing his muscles. Reformist newspapers – including Jame’e and Salam – were banned; one of Khatami’s closest political advisers, Saeed Hajjarian, who was accused by Khamenei’s son of birthing the reformist movement, was gunned down; and 24 Islamic Revolutionary Guard Corps (IRGC) commanders – who ultimately report to Khamenei – issued a public letter accusing Khatami of leading Iran into “anarchy.”To date, Khatami remains banned from leaving the country and is subject to a media blackout.Conservative firebrand president Mahmoud Ahmadinejad suffered a similar fate in his second term: Khamenei nixed his attempt to replace his intelligence minister Heydar Moslehi and a scheme to name his longtime consigliere Esfandiar Rahim Mashaei as first vice president due to his perceived challenging of the clerical establishment. After exiting the presidency, Ahmadinejad was humiliatingly warned against running again in 2017 by Khamenei. Recently the Supreme Audit Court found him guilty of the misuse of funds during his tenure.And if past is prologue, Hassan Rouhani may well become another persona non grata as long as Khamenei is supreme leader.Rouhani will also find it difficult to deliver on his promises of reform. During the campaign, he promised to lift the non-nuclear sanctions plaguing Iran’s economy – code for those measures tied to Tehran’s support for terrorism, regional meddling and human rights abuses. In his first press conference after winning reelection, Rouhani claimed that “[achieving] the [lifting of non-nuclear sanctions] is difficult but it is possible.” That’s not to mention his pledge to end the house arrests of former presidential candidates Mousavi and Mehdi Karroubi, and his call to drain the swamp of corruption in the judiciary.But, fundamentally, Rouhani remains hamstrung by the realities of a fifth column of deep staters who have a vested interest in his failure. The games have already commenced, with the embarrassing detention of yet another American hostage at a time when Washington was considering recertifying the nuclear deal, and the supreme leader’s mortification of Rouhani last month at a high-level gathering by saying, “Mr. President has talked at great length about the country’s economy, and, well, he’s said ‘this should be done,’ ‘that should be done’… but who is he addressing...?” Khamenei then answered his own question: “himself.” That’s on top of Rouhani’s war of words with the judiciary chief – accusing him of irregularities with state funds – and the retaliation with the arrest of the president’s brother, Hossein Fereydoun, on charges of financial malfeasance.These recent developments have served as a warning that the buck stops with the supreme leader, the judiciary and the security services – not president Rouhani – when it comes to real change.Lastly, the brief diplomatic rapprochement between Washington and Tehran is rapidly evaporating. With Washington levying new sanctions against Iran, US President Donald Trump dangling the possibility he will not recertify the nuclear deal and the Iranians retaliating by accusing the US of breaching its end of the bargain, a tit-for-tat dynamic has been unleashed. This state of play threatens to undermine Rouhani’s signature achievement, and in so doing neuter the fortunes of reformists within the regime.Henry Kissinger once said that Iran must decide whether it wants to be a nation or a cause. And if history is any guide, the cause will prevail in Khamenei’s Iran.The author is the policy director of United Against Nuclear Iran. He is on Twitter @JasonMBrodsky.