Some view him as a ruthless opportunist, others a convenient scapegoat for his superiors. But one thing is certain: Mohammed Dahlan, once considered the charismatic odds-on-favourite to succeed Yasser Arafat as leader of the Palestinians, is fighting for his political life.

Colleagues in the Fatah faction that now runs the West Bank expelled him from the group in June. They have accused him of everything from corruption to building his own private militia. In the attempt to disgrace - some might say smear - Mr Dahlan, they also leaked details of an internal report this month saying that he poisoned Arafat shortly before his mysterious death in 2004.

Neither the alleged evidence of the claims nor the report's authors have been made public, however. That has only added to speculation and unusual public bickering within Fatah over the downfall of the man who was once arguably one of the most feared people in the Gaza Strip.

"Some of them [Fatah members] pushed this false report to the media even though there is no proof substantiating any of it. On top of that, there still are no official accusations against him," said Sufian Abu Zaida, a well-known member of Fatah and friend of Mr Dahlan.

"It's all part of a dirty war against him."

The alleged "dirty war" began late last year following rumours that said Mr Dahlan, 49, had criticised the family business ventures of Mahmoud Abbas, Fatah's chairman and the president of the Palestinian Authority (PA).

Then a series of embarrassing castigations ensued. He was stripped of his security detail, forced by the PA to shut down a television station he owned and expelled from the faction amid a flurry of allegations that he and a group of political allies may have been planning a putsch.

The coup de grace came late last month when PA security forces raided his West Bank home near Ramallah. Media reported they arrested two dozen guards and aides, confiscating vehicles, weapons and 10,000 rounds of ammunition.

That was apparently enough for Mr Dahlan, who rose from tough circumstances in Gaza's Khan Younis refugee camp to eventually controlling the Palestinian enclave's Preventive Security Service. He has reportedly fled to Dubai.

Majid Shihade, a professor at the Abu-Lughod Institute for International Studies at the West Bank's Birzeit University, believes Mr Dahlan's undoing represents a significant victory for Mr Abbas after years of his Fatah colleagues jockeying against him.

"It's a consolidation of Abbas's power within Fatah and the Palestinian Authority," he said. "Dahlan went too far and started operating outside the PA. He had his own security group, which appeared to be under its own, autonomous authority."

This would not be the first time Mr Dahlan has been accused of challenging his superiors. He is said to have mounted more than one campaign against Arafat and by currying favour and, some say, ample funding from the United States, he had the financial leverage to act on his political ambition.

Mr Shihade said the Palestinian president likely felt compelled to act decisively against Mr Dahlan to present the appearance of a unified Palestinian front when they hope to win statehood recognition in September from the United Nations. "Otherwise," he added, "it would have been a lot more difficult to go on with the September plan."

Others, however, say the episode has more to do with the Palestinian president's long-standing inferiority complex than from any real threat presented by Mr Dahlan.

Lacking the charisma and popularity of Arafat, Mr Abbas has struggled to attract the sort of loyalty that the late president so successfully managed. One Palestinian political analyst said Mr Dahlan served as a useful example to be made of by the president. Blamed by many for allowing Hamas fighters to overrun his PA forces in Gaza four years ago, the outspoken Mr Dahlan was one of the few senior Fatah members who would not back down from public criticism of Mr Abbas.

"It's all about trying to quash dissent within Fatah, and Abu Mazen has done a good job at ensuring that," the political analyst said referring to Mr Abbas, adding that there was no evidence of Mr Dahlan attempting to assemble a private militia. "For somebody who is trying to do this in the West Bank, for someone who is already so reviled, this claim is laughable."

Yet that may explain why not all Fatah members uniformly rallied around Mr Dahlan's ouster. While the faction's main decision-making body, the Executive Committee, has reportedly thrown its backing behind Mr Abbas, its parliament-like Revolutionary Council issued a report disagreeing with the legality of Mr Dahlan's expulsion. Increasingly, his supporters in Fatah have spoken out against Mr Abbas.

For some, this may be evidence of a potential return by Mr Dahlan.

"He can open corruption files," said George Giacaman, a professor at Birzeit University's democracy and human-rights programme.

"He's still probably hoping to have a comeback. Lots of people have dirt on lots of other people, and he's in a good position to dig up dirt. So there are limits to what others can do to him."