Ahmad Chalabi (search) is an ambitious man who doesn't give up without a fight. The longtime Iraqi exile who always wanted to be prime minister was once also Washington's choice for the job, before it accused him of cozying up to Iran.

Now, the 58-year-old former mathematician is working the numbers, trying to entice more members into the winning Shiite alliance ticket and onto his side in the contest with Ibrahim al-Jaafari (search), a soft-spoken physician and interim vice president.

If Chalabi succeeds, it will be the culmination of a dizzying rise and fall and rise of a man who went from opposition leader to pariah to political player.

For the last 10 years he was the face of the opposition to Saddam Hussein in the United States as head of the Iraqi National Congress (search), one of the largest Iraqi opposition groups formerly in exile strongly supported by the Pentagon.

In the weeks after the 2003 invasion, Chalabi was the odds-on favorite to be his homeland's next prime minister. Now, he has enemies inside and outside of Iraq.

"He's certainly not a candidate who is neutral. He's someone that people have very strong views about, and this is a very delicate stage for Iraq," said Judith Kipper, director of the Middle East Forum at the Council on Foreign Relations.

Gunmen fired on his convoy in Baghdad last year, wounding two of his bodyguards. And he is wanted on charges of counterfeiting old Iraqi dinars, which were removed from circulation after Saddam's ouster last year. He remains at large because the interim Iraqi Interior Ministry has refused to follow up on the warrant.

His ties with Iran have riled Washington, once his biggest supporter, particularly in the runup to the U.S.-led invasion in March 2003. It has since accused him of inflating reports of Saddam's illegal weapons programs, Washington's main justification for the war. Relations between Chalabi and the United States reached an all-time low last year when Washington accused him of leaking intelligence secrets to Tehran, a charge Chalabi denied.

Then there are the Jordanians. In 1992, Chalabi was convicted of fraud in absentia as part of a banking scandal in Jordan. He was sentenced to 22 years in jail, but hasn't served a day.

On Monday, Jordan's government reacted with vehement condemnation to the speculation that Chalabi could be Iraq's next premier — and said Amman would hardly look forward to dealing with an Iraqi government run by a wanted man.

"We will not be thrilled if he assumes a government position," said Asma Khader, a spokeswoman for the Jordanian government. "But," she added, "this is an internal matter for the Iraqis."

Iraq's fragile political condition and tenuous security situation may be Chalabi's greatest obstacle, if those in the alliance choose al-Jaafari simply because he is more popular. Also pivotal is the endorsement of Grand Ayatollah Ali al-Sistani (search), an integral element for either candidate's success.

Al-Jaafari seemed all but certain to assume the post after his main opponent, Adil Abdul-Mahdi (search) of the Supreme Council for Islamic Revolution in Iraq (search), dropped out. But instead of withdrawing to preserve unity within the alliance — the reason given by Abdul-Mahdi — Chalabi appears determined to battle it out.

Chalabi is a man who likes working with numbers. The gamble may turn out to be a calculated risk, and Chalabi could succeed elsewhere if he loses the premiership — perhaps a powerful ministry post.

Or maybe this time, the odds will swing his way.