Iran's ruling establishment has moved to prevent infighting by allowing only a handful of conservatives loyal to the all-powerful supreme leader to contest next month's presidential election, analysts say.
This paves the way for the most powerful political institutions to be completely run by individuals hand-picked by Ayatollah Ali Khamenei, the country's ultimate decision maker, or by those obedient to him.
The attempt to consolidate more power comes at a time when Iran, at loggerheads with world powers over its nuclear ambitions, is struggling to cope with harsh economic sanctions targeting its vital oil income.
"All candidates with a chance of winning are either related to the leader or to the security apparatus," one Western diplomat, speaking not for attribution, told AFP.
"It is not in shades of grey, but all black."
The Guardians Council -- conservatives appointed directly or indirectly by Khamenei -- on Tuesday revealed a list of eight candidates cleared to stand for president on June 14, after vetting their credentials and loyalty to the revolution and its leader.
Many had correctly anticipated the exclusion of Esfandiar Rahim Mashaie, a divisive figure close to incumbent President Mahmoud Ahmadinejad.
But what shocked most people was the one name not on it: Ayatollah Akbar Hashemi Rafsanjani, a pragmatist two-time president from 1989 to 1997.
Rafsanjani, 78, as a founder had been in the echelons of power since the Islamic regime's inception.
His decision to enter the race had polarised Iran's political system, with marginalised reformists backing him and hardline conservatives launching a campaign to discredit his candidacy.
Rafsanjani's exclusion shows that the regime's inner circle, stacked with Khamenei loyalists, is diminishing in size, observers say.
"The political spectrum in Iran continues to shrink and shift to the right," Trita Parsi of the National Iranian American Council advocacy organisation in Washington told AFP.
Khamenei is now tightening his grip and eliminating "any potential internal competition" ahead of a new government expected in early August, Parsi said.
For years Rafsanjani was considered a kingmaker because of his vast political sway. But his stock plummeted in 2005 when his botched attempt for the highest elected office was thwarted by Ahmadinejad.
Four years later, as he navigated the aftermath of Ahmadinejad's 2009 re-election, Rafsanjani fell from grace after siding with the pro-reform movement that staged massive street protests alleging electoral fraud.
The protests provoked a heavy-handed state crackdown leaving dozens dead and hundreds behind bars, shaking the foundations of the Islamic regime and delivering a blow to the prestige of Khamenei who threw his support behind Ahmadinejad and publicly shunned Rafsanjani.
Khamenei then called on the opposition to accept the election result, which the so-called Green Movement and its leaders -- Mir Hossein Mousavi and Mehdi Karroubi, now both under house arrest -- had rejected.
"Given what happened in 2009, they're trying to make this election more predictable," Karim Sadjadpour, an Iran expert and senior associate with the Carnegie Endowment for International Peace, told AFP.
Sadjadpour said that with a loyal president, Khamenei's grip on power could become complete.
"Iran's most powerful political institutions, the Revolutionary Guards, the judiciary, the Guardian(s) Council, the Experts Assembly, and the parliament are (already) controlled by individuals hand-picked by Khamenei or obsequious to him," he said.
Rafsanjani's exclusion has eclipsed the disqualification of another would-be frontrunner: Mashaie, whose poor reputation among regime insiders would be unrivalled if it were not for his main ally, Ahmadinejad.
Mashaie -- the bane of conservatives for views seen as too liberal and his alleged intent to erode the influence of clergy on decision making in the Islamic republic -- could have gained traction, campaigning alongside Ahmadinejad.
Unlike Rafsanjani, who has vowed not to protest, Ahmadinejad on Wednesday said he would fight Mashaie's disqualification through Khamenei, who has in the past issued decrees reinstating presidential candidates.
But analysts say the exclusions pose a lesser threat to the regime than allowing heavyweights to challenge the hardliners.
"Between an open ballot and 'zero risk', the supreme leader chose the latter," said the diplomat.
Another Tehran-based diplomat, also speaking not for attribution, said: "The regime does not want to take any chances. The list of eight poses the slightest possible risk."