The biggest Sunni Muslim political group dealt a blow to ballot plans by withdrawing from the campaign because of the lack of security, while a suicide car bomber killed 15 people in an attempt to assassinate the head of Iraq's strongest Shiite party before parliamentary elections next month.
The bomber tried to drive his car through the gate at the home of Abdul Aziz al-Hakim, leader of the Supreme Council for the Islamic Revolution in Iraq, but detonated his explosives when guards blocked the way.
Fifteen people died and at least 50 were wounded in the explosion, which shook Baghdad's Jadiriyah district and sent a cloud of smoke billowing into the sky, police Captain Ahmed Ismail said. Thirty-two cars on the street were destroyed or damaged. Al-Hakim, who was inside, was not hurt.
Al-Hakim heads the 228-candidate list of the United Iraqi Alliance, which includes parties and individuals from all Iraqi ethnic and religious groups but is dominated by Shiites, who account for about 60 percent of the country's population. Backed by Iraq's top Shiite cleric, Grand Ayatollah Ali al-Sistani, the coalition is widely expected to dominate the postelection constitutional assembly and play a key role in formulating Iraq's new national charter.
Just hours after the blast, the leader of a moderate Sunni bloc, the Iraqi Islamic Party, announced that the group had reversed its earlier decision to take part in the Jan. 30 elections.
"The security situation keeps going from bad to worse and has to be dealt with," Mohsen Abdel-Hamid said.
The two events underlined the difficulties that the insurgency is causing for Iraq's interim government and the US-led military coalition in trying to hold credible national elections -- the first free ballot since the overthrow of the monarchy 46 years ago.
Continuing attacks and intimidation have led senior Sunni political and religious leaders to call for a postponement of the vote until the insurgency is brought under control.
The Iraqi Islamic Party said its decision to pull out of the race did not mean it would not take part in a future ballot.
"The party's desire is to take part in the future, should the requirements for its success be available," it said.
Party Secretary General Tarek al-Hashemi acknowledged the withdrawal would leave minority Sunnis underrepresented in the assembly elected Jan. 30, but added: "We believe when a house is on fire, you should first put out the fire before working on decorating and arranging it."
Shiites comprise by far the biggest community in Iraq, with Sunni Arabs and ethnic Kurds making up 20 percent each. Many people in Iraq and abroad fear the legitimacy of the election will be brought into question if Sunnis refrain from voting.
Shiite political and religious leaders also have sharply criticized the US-led response to the insurgency, saying Iraqis themselves would have been more effective in countering the mainly Sunni insurgency. But Shiite leaders also strongly back going ahead with next month's vote even though they have been repeatedly targeted by the insurgents since the ouster of Saddam Hussein.
Since the modern Iraqi state was set up by British colonialists in the aftermath of World War I, it has always been dominated politically and economically by the Sunni minority, and Shiite leaders are eager to translate their numerical superiority into political power.