“I did more than anyone else in persuading the U.S. to get rid of Saddam,” said Ahmad Chalabi, sitting in the dark next to his empty swimming pool.

Soon the American troops that did so will be gone. Mr. Chalabi, as perplexing and contentious as he was in the prelude to the war, will be staying behind, perhaps finally with an official grasp on power in Iraq that has always eluded him.

He was a candidate in the recent elections, his alliance of Shiite parties with ties to the radical cleric Moktada al-Sadr is running third in the balloting, and he could well claim a seat in Parliament — something he did not accomplish in the last parliamentary election, in 2005, when his party, the Iraqi National Congress, received just 30,000 votes of 12 million.

His electoral prospects aside, Mr. Chalabi, at 65, has improbably — and controversially — reinserted himself in Iraqi politics. His role before the parliamentary elections in disqualifying nearly 500 candidates with ties to Saddam Hussein’s Baath Party helped raise fears about a rigged election as well as worries of disenfranchisement among Sunni Arabs, who are a minority here but were politically ascendant under Saddam Hussein’s dictatorship. “Baathism in Iraq equals Nazism in Germany,” he said.

When he appeared recently at the government election commission, amid a ballot-counting process that was becoming more opaque by the day, he stoked conspiracy fears of political meddling among a population prone to believe them — even though political parties have a right to have representatives present, and Western diplomats have said that nothing sinister was afoot with Mr. Chalabi’s appearance.

It has been six years since Mr. Chalabi was the guest of President George W. Bush at the State of the Union address. Five months after that his home was raided by the Americans, who suspected him of spying for Iran. Then the sectarian war began and tens of thousands of Iraqis died.

In decades of exile in London, he made a fortune in banking and real estate, though not without the usual element of controversy; in 1992 he was convicted in absentia of bank fraud in Jordan. He did return to London during the sectarian war, but says it has been more than a year since he has been there.

Mr. Chalabi was born into a prominent and wealthy Iraqi Shiite family in Baghdad, but left in 1956, years before Saddam Hussein assumed power. He returned in 2003 but quickly ran afoul of the Americans, and the animosity still simmers. In February, Gen. Ray Ordierno, the top commander in Iraq, said Mr. Chalabi and his partner on the panel that disqualified the parliamentary candidates were “clearly influenced by Iran.”

Hazim al-Nuaimi, a political science professor in Baghdad, said Mr. Chalabi, “has very strange instincts for the winning hand in political poker.”

“He felt the American role decreasing in the country and the Middle East and he went to play another winning set of cards, which is the Iranian cards,” Mr. Nuaimi said.

Mr. Chalabi says he has had close relationships with both the United States and Iran, but admitted that relations these days with Americans are “in abeyance.” But he said he was still friends with two of his former neoconservative allies in the Bush administration, Paul D. Wolfowitz, the former deputy secretary of defense, and Richard N. Perle, who was chairman of the Defense Policy Board.

MR. CHALABI will not discuss his political ambitions, but few here doubt that he wants to be prime minister. In a mocking tone, he derides newspaper reports that, he says, paint him as a man of “unbridled ambition” who “is determined to be prime minister.”

“There is no such thing,” he said.

And despite his incongruities — a former American ally now cozy with Iran; a secular Shiite, wealthy and educated at M.I.T., now in lockstep with radical Islamist parties — he is skilled at maneuvering himself into a power broker’s role, even if it is unclear how popular he is among the Iraqi people. The early results of this election tend to confirm that he has managed the feat again.

“Anyone who calls him over and done is always going to be wrong,” said Aram Roston, an author who wrote a biography of Mr. Chalabi called “The Man Who Pushed America to War.”

And while his allegiances seem constantly in flux, he can inspire deep loyalty. One of his closest advisers remains Francis Brooke, an American who met him in 1991 through C.I.A. connections and lives in a house in Georgetown owned by Mr. Chalabi’s political organization.

“He is a Machiavellian politician who has no respect for any principle or any ideology,” said Professor Nuaimi. “Politics to him is just bargaining and deals.”

Mr. Chalabi has been accused of opportunism in forging his alliance with Shiite extremists, but he said that was not his intent. “Sectarian politics gets votes in Iraq,” he said. “But sectarian government fails in Iraq.”

THE de-Baathification controversy, which caused an uproar both in the West and among Sunnis, was actually, say some Western diplomats now, a masterstroke by Mr. Chalabi. It cemented his alliance with Shiites, tapping into their still bubbling reservoir of resentment here toward the indignities of living under Mr. Hussein.

“He’s a hero, Chalabi, because he uprooted the Baathists,” said Ahmed Khalaf, 33, who works in a grocery store in Sadr City, a predominantly Shiite neighborhood of Baghdad. “Any Baathists he found, he tore them out of the government.”

Another Sadr City resident, Abu Ahmed Hassan, 50, called Mr. Chalabi “beloved.” He said, “The Americans hate him, the Jordanians arrested him. So he must be good.”

Underscoring the complexities of Mr. Chalabi’s political character, it is easier to find an Iraqi to say something nice about him on the hardscrabble streets of Sadr City than it is in the halls of the Iraqi Hunting Club, a social club for Baghdad’s elite in the wealthy Mansur district. It is near one of Mr. Chalabi’s homes, and served as a base of operations for him after the 2003 invasion. He also held events there during the recent campaign.

“If Ahmad Chalabi walked in here you wouldn’t see him because he would be surrounded by so many guards,” said Abu Shakeen, 38, on a recent afternoon.

“First, he’s a businessman,” he said. “He knows how to use politics for his own gain in business.”

And he knows how to manipulate images to make a point. A few days ago, Mr. Chalabi hosted a group of Iraqi amputees at his compound to be fitted with prosthetic limbs, paid for by his family’s charity. “American troops shot all these guys,” he said.

Many of the injured had actually lost their limbs during the war between Iraq and Iran in the 1980s. But one, Haider Kareem, 38, said he lost his right leg in 2005 when he was caught in the middle when an American convoy opened fire.

While seven years have passed since the invasion, Mr. Chalabi still proudly takes credit for helping craft the argument that justified it. Of course, much, if not most of that artifice, crumbled after intelligence about Iraq’s weapons programs — some of it provided by Mr. Chalabi’s Iraqi National Congress — proved to be entirely wrong.

Nevertheless, he said the war still made sense. “The world is a safer place now, and the U.S. gave us the gift of democracy.”

Anthony Shadid and Riyadh Mohammed contributed reporting.