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If He Did It

In the first round of voting in 2005, the three conservative candidates for Iran’s presidency — Mahmoud Ahmadinejad, Ali Larijani and Mohammad Baqer Qalibaf, got a collective 41 percent of the vote. Last Friday, ostensibly, Ahmadinejad got 63 percent of the vote. Where exactly did those extra votes come from?

One way to address this question is by means of multiple regression analysis. We can take the vote shares for the seven candidates in 2005, and compare in each of Iran’s 30 provinces to the share of the vote received by each of the four candidates this year. I will weight this regression by the square root of the number of votes in each province, to give more emphasis to those with larger vote totals.

The way to read this table is from left to right. If we look at the second row down, for example — those votes which went to Ali Larijani in 2005 — we estimate that 83 percent of his voting block went to Ahmadinejad, 16 percent went to Mousavi, and 1 percent went to Karrobui. Those results are not surprising; Larijani was a conservative, and so is Ahmadinejad.

Likewise, Ahmadinejad apparently picked up most of the vote from Mohammad Baqer Qalibaf, the conservative former mayor of Tehran. He also kept most of his own vote. Mousavi, meanwhile, picked up most of the vote from Mohsen Mehralizadeh and Mostafa Moeen, two reformist candidates. Those results aren’t surprising either.

Let me warn you, before proceeding further, that the margins for error on this type of analysis are quite high. It should not be considered definitive. We would need to look at city-level data to come up with more robust estimates.

But with that disclaimer, at least one result is rather surprising. Namely, Ahmadinejad appeared to pick up most of the vote from Mehdi Karroubi, who is routinely described as the most liberal of the candidates. This is in spite of the fact that Karroubi himself was on the ballot this year; he appeared to retain only about 5 percent of his own vote.

Renard already detected this pattern, so I am not really telling you anything new. But it seems to me to be the key to explaining the Iranian election — whether it was legitimate or whether it was rigged. Ahmadinejad won all of the provinces that Karroubi won in 2005, and his cumulative share of the vote in these 11 provinces was 66 percent, exceeding his overall total. In the province where Karroubi did best in 2005, his home province of Lorestan, Ahmadinejad got some 71 percent of the vote.

Now, most of those provinces where Karrobui did well in 2005 are rural, and it’s possible that the rural tilt toward conservative candidates was greater in 2009 than in 2005. As I mentioned earlier, Ahmadinejad actually didn’t do that badly in Iran’s most urban province, Tehran, in 2005, but he performed relatively poorly there last week. If Ahmadinejad won the election, he did it by winning over these rural Karrobui voters. And if he stole it, those were the votes he stole or intimidated.

A secondary factor in Ahmadinejad’s purported success was his ability to capture most of the vote from Akbar Hashemi Rafsanjani, a moderate (by Iranian standards) whom Ahmadinejad defeated in the 2005 run-off. Rafsanjani won three provinces in the first round in 2005: Kerman, Zanjan and Gilan. Ahmadinejad ostensibly won all three, grabbing 78 percent of the vote in Kerman, 77 pertcent Zanjan and 68 percent in Gilan. Kerman, indeed — Rafsanjani’s best province in 2005 — was Ahmadinejad’s best in 2009.

This is arguably a bit easier to digest than Ahmadinejad’s success among Karroubi voters. Rafsanjani was Preisdent of Iran between 1989 and 1997 and was the closest thing the voters had in 2005 to an incumbent; Ahmadinejad, of course, was the incumbent this year. However, Ahmadinejad and Rafsanjani have quite a rivalry, with Ahmadinejad calling Rafsanjani a “puppet-master” and Rafsanjani calling Ahmadinejad a liar on the eve of the election.

But this is Mahmoud Ahmadinejad’s story, and we’re guessing that he’s sticking to it.

Nate Silver is the founder and editor in chief of FiveThirtyEight.