Thirty years after the Islamic revolution, Ayatollah Khamenei is looking to remove rival old-guard leaders – including Mir Hossein Mousavi.
Street clashes between security forces and supporters of challenger Mousavi picked up after dark on Sunday after President Ahmadinejad addressed thousands of his supporters in Tehran.
Street demonstrations quieted ahead of intensely anticipated presidential vote on Friday.
President Mahmoud Ahmadinejad faced off against one of his three opponents, Mir Hossein Mousavi, Wednesday night in the second of six debates leading up to June 12 elections.
President Mahmoud Ahmadinejad's hard-line allies and other conservative factions are expected to win a majority in the 290-seat parliament.