At press time last weekend, Tehran felt something like Miami circa November 2000. After an intensely fought campaign for president, election officials had declared the incumbent, Mahmoud Ahmadinejad, the victor with nearly two thirds of the vote. Supporters of his main opponent, reformist Mir Hossein Mousavi, were furious, convinced that the results had been rigged. On Saturday, hundreds were beaten by riot police after taking to the streets in protest.

When Ahmadinejad is eventually sworn in, as seems likely, the question is who, if anyone, might provide a credible internal opposition. Mousavi, who often seemed rattled in his fierce TV debate with Ahmadinejad two weeks ago, is unlikely to square off against the president. The more likely candidate to step up is Ali Akbar Hashemi Rafsanjani, a former president and one of Iran’s richest men, who threw his vast financial and political resources behind Mousavi. For Rafsanjani, who suffered a humiliating loss to Ahmadinejad in the 2005 election, the campaign was clearly personal. And he could prove a genuine threat to the president: Rafsanjani heads both the Assembly of Experts and the Expediency Council, which together elect and advise the Supreme Leader, and, more important, he knows how to work the system. After Ahmadinejad accused him and his sons of corruption during the TV debate, Rafsanjani wrote an unprecedented letter to Supreme Leader Ayatollah Ali Khamenei, asking him to “prevent the spread of dangerous provocations.” Khamenei listened: he invited Rafsanjani to his home, and the two met for three hours. While Khamenei may not have wanted a serious rival like Mousavi in office, he won’t necessarily want to alienate his millions of supporters, and Rafsanjani could help bridge the divide.

Rafsanjani would also prove essential in any outreach to the United States, which, counterintuitively, is more likely with Ahmadinejad’s reelection. Khamenei might have had qualms about allowing a more liberal president to initiate talks, but in Ahmadinejad he has a tough negotiator sure to drive a hard bargain on all issues, including the country’s nuclear program. And it was on Ahmadinejad’s watch, after all, that the U.S. and Iran had their most extensive meetings in 30 years, between their ambassadors in Baghdad. Rafsanjani would be a useful asset in such talks. He helped negotiate the release of U.S. hostages in Lebanon 20 years ago, hoping for a U.S.-Iran détente. Washington didn’t reciprocate at the time. But now that the Obama administration has stretched out its hand, Rafsanjani is likely to push Khamenei to grasp it.