BAGHDAD, Iraq, Nov. 13 - As Ayad Allawi, Iraq's interim prime minister, starts to position his party for the coming national elections, rising public denunciation of the invasion of Falluja by prominent Iraqi groups has put his political support at risk when he needs it most.
Dr. Allawi will almost certainly run for one of the 275 national assembly seats up for grabs in January. His party, the Iraqi National Accord, and other politicians have begun jockeying to form coalitions in order to secure as many votes as possible.
But depending on the outcome in Falluja, Dr. Allawi, 58, could find himself without a significant political ally. Even if the battle ends quickly and without a large number of civilian casualties, Dr. Allawi, by ordering the invasion, has affirmed his image as an ardent supporter of the American presence here. That is enough to keep politicians from wanting to be linked to him.
"The Allawi government has full responsibility for whatever happens in Falluja," said Redha Jowad Taki, a senior official in the Supreme Council for the Islamic Revolution in Iraq, a powerful Shiite party.
"Support for the government has been eroding since last summer," Mr. Taki said. "It had big backing among the people then, but it's failed to deal with gangs of terrorists, and that has led to the loss of support."
Further, public condemnation of Dr. Allawi's role in the invasion has come from across Iraq's political spectrum.
The leading group of Sunni clerics, the Muslim Scholars Association, singled out Dr. Allawi for criticism last week when it called for a boycott of elections to protest the offensive.
"The Iraqi clerics place on the government of Ayad Allawi the entire legal and historical responsibility for what Falluja is going through, which is genocide at the hands of the occupiers," said Harith al-Dhari, the association's leader.
What may do more political harm to Dr. Allawi, who is a Shiite, is the fact that Shiite leaders are also condemning the invasion. Shiites make up at least 60 percent of Iraq and are the largest voting bloc.
The most powerful Shiite cleric, Grand Ayatollah Ali al-Sistani, said through a spokesman on Friday that the security issue should be solved through peaceful means. Representatives of Moktada al-Sadr, the rebel Shiite cleric, are calling on Iraqis not to take part in the offensive.
"Don't stain your hands with Iraqi blood," an aide to Mr. Sadr, Sheik Abdul Hadi al-Daraji, said in front of thousands of worshippers at a Baghdad mosque on Friday. "We demand you stop fighting against your brothers in Falluja."
The pressures on Dr. Allawi have increased enormously over the week, with his backing of the American forces now costing him personally as well as politically. On Tuesday night, insurgents kidnapped a first cousin, Ghazi Majeed Allawi, the cousin's wife and a daughter-in-law. A militant group called Ansar al-Jihad posted an Internet message the next day saying it would behead the captives in 48 hours if Dr. Allawi did not halt the invasion of Falluja and release all prisoners in Iraq.
The deadline expired sometime on Friday. No word has emerged of the fates of the hostages.
Some Iraqis, mostly Shiites and Kurds, do support the Falluja invasion, which is aimed at wiping out resistance from Sunni insurgents. The problem is that with elections coming up, even those supporters could publicly denounce the offensive no matter what they really think, because siding with the American-led forces could lose them votes. So Dr. Allawi finds himself increasingly alone in the political arena.
Since taking office in June when the United States handed formal sovereignty to Iraq, Dr. Allawi has struggled to portray himself as a representative of the Iraqi people rather than of the American government. His background as an exile with close ties to the Central Intelligence Agency has made that difficult. The decision to invade Falluja finally forced him into a corner. He had to say publicly that the decision, not very popular among Iraqis, was fully his own.
It is unclear how much power the Bush administration gave Dr. Allawi in setting the timing of the invasion. A senior Pentagon official said the timing "was a mutual decision, involving the White House and Allawi, and everyone else in between," he said.
A senior military official in Iraq said that Dr. Allawi had insisted on starting the offensive by Nov. 12 so there would be enough time to wrap it up by Nov. 22, when Dr. Allawi and other Iraqi officials are to attend a conference in Egypt on the future of Iraq.
Dr. Allawi became testy when asked at a news conference last week whether his decision to invade Falluja would deepen a divide in Iraq between those people who back the resistance and those who oppose it. He tried to portray his decision as one with immense popular support.
"I think there is a misperception on your part," he said to a reporter. "There is a division between the Iraqi people and the terrorists. We are after terrorists. We are not after anyone else."
Even if Dr. Allawi had never ordered an invasion of Falluja, his party might have had a tough time finding political allies. It is secular, and Iraq is becoming an increasingly religious society.
Even more troubling for many Iraqis, the party is made up of many former Baath Party officials, including Dr. Allawi. Asked on Saturday how Dr. Allawi was taking the political heat over his order to invade Falluja, one of his confidants, Kassim Daoud, the national security adviser, shrugged it off.
"Listening to criticism is practicing democracy," Mr. Daoud said. "We don't mind being criticized by any party."
Robert F.Worth contributed reporting from Falluja for this article, and Eric Schmitt from Washington.