According to preliminary and still incomplete data, which may undergo minor changes, the conservatives won 75 percent of the seats in the Mejlis.
They won in Tehran, Qom, Tabriz, Mashhad and other provincial centers, even in some places where Ahmedinejad triumphed in the 2009 elections.
The split between conservatives and nationalists occurred last year, when President Ahmedinejad tried to challenge Supreme Leader Ayatollah Ali Khamenei's undisputed authority over the country's foreign policy and intelligence services.
In the clerical structures, Ahmadinejad's populist nationalism is perceived as a threat to the Islamist republic, whose foundations were laid by Ayatollah Khomeini in 1979.
The turnout in the elections was very high, 64 percent, although the leaders of the reformist groups called on their supporters to boycott the vote.
In Tehran, regardless of internal divisions, this is perceived as a great success, in fact as a response to the West, which is attacking Iran because of the disputed nuclear program and which has therefore tightened economic sanctions on Tehran.
"The high turnout of citizens is a slap in the face to Iran's enemies," said Interior Minister Mohammad Najjar, specifically mentioning Americans and Zionists (Israelis).
The final results of the parliamentary elections are expected today or tomorrow, but it is already certain that Ahmadinejad has lost the majority support in the parliament, which has 290 deputies.
His popularity has also declined due to the economic crisis deepened by new sanctions from Western countries, which accuse Tehran of working on the production of an atomic bomb. In Iran, they persistently deny it.
At a time when Iran is exposed to severe Western pressure due to the production of nuclear weapons, the two elites - Khamenei's conservatives and Ahmadinejad's nationalists - will not tighten their relations, analysts say.
The president will end his second and last term in 2013, but surely with weakened positions. No change is expected in the country's foreign policy either, since religious leader Ayatollah Khamenei has always had the last word in that area.
"It seems that the political era of Ahmadinejad is slowly coming to an end in the history of Iran," says David Hermidas Bavand, a political analyst in Iran.
Others, however, warn against jumping to conclusions.
"The elections confirmed that the rift between the leading elites has deepened. However, this does not mean that Ahmedinejad's block has been disbanded. We should wait until the beginning of June when the new parliament should be constituted," assesses analyst Hamid Farahvashin, agencies report.
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