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Last March, Iran's President Mahmoud Ahmadinejad was summoned by an angry parliament to answer questions about his economic policies, a banking fraud perpetrated by some of his allies, and his defiance of Supreme Leader Ayatollah Ali Khamenei. Mr Ahmadinejad made light of the questions, delivered irreverent one-liners, and questioned the intelligence of the MPs - most of whom hail from conservative and hard-line camps.

The parliamentary showdown, aired live on state radio, offered a window into the power struggle between Mr Ahmadinejad and his former allies in the conservative camp, most of whom stood firmly behind the president in his controversial 2009 "re-election" that resulted in massive street protests amid allegations of fraud. By March 2012, Mr Ahmadinejad had...