From an excellent article in the Washington Post:

The election results in Iran may reflect the will of the Iranian people. Many experts are claiming that the margin of victory of incumbent President Mahmoud Ahmadinejad was the result of fraud or manipulation, but our nationwide public opinion survey of Iranians three weeks before the vote showed Ahmadinejad leading by a more than 2 to 1 margin — greater than his actual apparent margin of victory in Friday’s election.

The fact that, in the run-up to the election, expectations were low for any change in Iran is also pretty good evidence that what we are seeing is, sadly, less a reflection of majority opinion than a vocal, and highly motivated minority.  The implications are a little scary just weeks after the anniversary of Tiananmen…

The article concludes with some political dangers:

Allegations of fraud and electoral manipulation will serve to further isolate Iran and are likely to increase its belligerence and intransigence against the outside world. Before other countries, including the United States, jump to the conclusion that the Iranian presidential elections were fraudulent, with the grave consequences such charges could bring, they should consider all independent information. The fact may simply be that the reelection of President Ahmadinejad is what the Iranian people wanted.

Update:  There may be reason to remain suspicious even in light of this poll.  See Marciano’s comment below.