By Max Fisher

Iranian presidential candidates debated Friday on national TV in Tehran. (AP Photo/Islamic Republic of Iran Broadcasting, Mehdi Dehghan)

For all the authoritarianism that has creeped into Iran's political system, particularly since the protests and crackdowns after the 2009 election, Tehran politics still have more dissent and fewer taboos than many Americans might expect. Friday's presidential debate, the third and final before an election later this month, had the candidates openly sparring on some of the country's most sensitive issues, including nuclear negotiations with the West and crackdowns on student protests.

This debate doesn't mean that whoever wins the election could singlehandedly change the country's course on these issues or would even want to, but it is a reminder that Iran's political system is not always monolithic. Such internal dissent is limited, though: A judicial body allied with the supreme leader blocked former president Akbar Hashemi Rafsanjani and others from running in the election, for example.

The debate over nuclear issues seemed to turn on a premise, emphasized by several of the candidates, that the negotiations with the West and with international institutions over Iran's nuclear program have been a failure. That's a pretty clear implicit critique of Supreme Leader Ali Khamenei's emphasis on stubborn resistance to outside pressure, even if the candidates did not mention Khamenei himself. Their discussion on student protests was a little less clear, but the candidates seemed eager to distance themselves from the crackdowns, implying that, at the very least, they do believe that popular opinion is hostile to such repression. We might assume as much in the contemporary American context, but recall that in many countries, including the United States, lots of people tend to support "law and order" over protest rights during times of unrest.

Here are few interesting moments from the debates, as noted by several Iran-watchers on Twitter. As you can see, whatever the result of the election itself, most of the candidates aren't interested in just rubber-stamping Khamenei's policies. They're debating freedom of speech, nationalism, confrontation with the West, diversity and other complex issues.