Iran's political landscape has become increasingly divided during controversial President Mahmoud Ahmadinejad's second and final term. But as a diverse array of candidates to replace him takes shape, nearly all the contenders seem united on one thing: attacking the president's legacy.

The eventual winner of the June election will wield influence over the direction of negotiations on Iran's nuclear program, a topic of immense importance to the U.S. In Iran, however, the biggest election issue is the sagging economy, and most among an emerging list of about 20 candidates argue that it has been harmed as much by Ahmadinejad's tenure as by international sanctions.

The growing field of hopefuls is generating fresh popular interest in an election that few believed would be competitive just a short while ago. That is in large part because candidates must be approved by Iran's Guardian Council, a powerful body of clerics and jurists, half of whom are appointed by Supreme Leader Ayatollah Ali Khamenei.