Next month, Iran may enter its most heated political phase since the 1979 revolution when the country is due to elect a new president.

Incumbent president Mahmoud Ahmadinejad is legally barred from pursuing a third term. His successor will have to cope with many economic and foreign policy challenges created or at least aggravated during his eight years in power.

Adding to the gravity of the situation is a conflict between Ahmadinejad and the supreme leader, the continued inflexibility of Iran’s foreign politics and a deterioration in relations between the fathers of the revolution, former presidents Mohammad Khatami and Akbar Hashemi Rafsanjani on the one hand and incumbent supreme leader Ali Hosseini Khamenei and Ahmad Jannati Massah, chairman of the Guardian Council, on the other.

The Guardian Council functions as a legislative senate and Constitutional Court at once and must also approve candidates before they can stand for political office. Members, appointed by the supreme leader and parliament, are usually clerics and lawyers. The president, by contrast, is elected through a popular vote.

June’s presidential election will be the first held after the hotly contested vote of 2009 when the reformist opposition split, Ahmadinejad was reelected and the main opposition candidate, former prime minister Mir-Hossein Mousavi, won just one in three votes according to the official results.

Ahmadinejad contained the subsequent unrest — hundreds of thousands of Mousavi’s supporters alleged fraud — at the expense of the reformists’ participation in political life with a campaign of arrests, exiles and house arrests.

The most prominent clash was among conservatives, however, who split into two factions: neoconservatives led by Ahmadinejad and fundamentalists led by the supreme leader. The conflict stemmed from a dispute about the distribution of power between their respective parts of the executive branch as well as Ahmadinejad’s policies.

Iran’s economy has all but collapsed under the weight of international sanctions, enacted to discourage it from developing a nuclear weapons capability, as well as its own mismanagement. Oil sales are down by half. Inflation might exceed 50 percent although estimates vary and the government put the rate at 31.5 percent in March. The official unemployment rate exceeds 12 percent.

Iranian politics has become more divisive. Whereas competition in the years following the 1979 revolution was largely limited to conservatives versus reformists, competing alignments within each faction have complicated the picture.

The struggle for the presidency will nevertheless be among the conservatives: between Ahmadinejad’s supporters and those of the supreme leader’s. The latter appear to have the advantage since last year’s parliamentary election when 68 percent of new legislators were Khamenei loyalists.

Khamenei seeks to avoid a repeat of the mass demonstrations that swept Iran after the 2009 election which were considered a threat to the survival of the regime. He also wants a loyalist elected who can unify the ruling powers and lead the country out of its present economic and political turmoil.

That is unlikely. Ahmadinejad’s supporters, even if they lose the upcoming vote, will not disappear. The internal upheaval, moreover, will make it all the more difficult for the next president to make any progress in international talks about the country’s nuclear program, thus prolonging its suffering as sanctions will remain in place.

Whether Iranian foreign policy as a whole will shift is more doubtful. Ahmadinejad’s legacy will be one of isolating the Shia republic while seeking to influence political events in countries ranging from Bahrain to Iraq to Syria, often against the backdrop of its struggle for regional hegemony with Sunni powers like Saudi Arabia.

Few, if any, of the foreign policy initiatives pursued during Ahmadinejad’s tenure bore fruit. His successor will have to rebalance Iran’s international relations.

If, as expected, that is a Khamenei loyalists, it might also reveal whether Iran’s foreign policy mishaps were truly Ahmadinejad’s or the supreme leader’s all along.