A four-day holiday and a strict 10 p.m. to six a.m. curfew dramatically lessened traffic in Baghdad Friday.
The city's usual chaotic streets were almost empty of people and cars, as thousands of Iraqi police and army troops fanned out, manning checkpoints and enforcing new security rules, which will be in effect for the next three days.
Iraq's international borders have been closed, and no one can travel between Iraq's provinces. No civilian flights are being allowed in or out of Baghdad's international airport until Monday morning.
On voting day, all civilian vehicles will be banned from moving around Baghdad, and car traffic will be severely restricted in most cities in Iraq. Voters will have to walk on foot to polling centers, navigating around kilometers of barbed wire and concrete barriers placed on the roads and around polling sites.
Iraqi and coalition officials are hoping the tough measures will deter insurgent groups, opposed to Iraq's political process, from trying to wreck Saturday's referendum.
Pre-referendum violence has already killed nearly 450 people in the past two weeks. But most Iraqis say the threat of more attacks will not prevent them from exercising their right to vote. An estimated 15.5 million Iraqis are expected to visit 6,100 polling centers across the country.
Iraqi Kurds and the vast majority of the country's Shi'ite Muslims are expected to vote in favor of the constitution, which was largely written by Shi'ite and Kurdish legislators who dominate Iraq's interim government.
For weeks, thousands of posters and banners urging a "yes" vote have adorned walls and shop windows in cities across the Kurdish north and mostly-Shi'ite areas throughout the country.
During Friday prayers at the al-Rahman mosque in the Mansour district of Baghdad, Shi'ite cleric Abbas al-Musawi reminded several hundred of his followers that they have a religious duty to cast a "yes" vote.
The cleric says the ruling council of Shi'ite clerics in Najaf, including Grand Ayatollah Ali al-Sistani, has issued an edict, instructing every Iraqi man and woman to vote for the constitution. He says this is an order, which must be carried out.
There are also posters and banners plastered on walls and windows in Sunni-dominated areas of Iraq. But they urge Iraqis to boycott the referendum or to vote down the charter.
Sunni Arabs, who lost power after the fall of Saddam Hussein and form the backbone of the country's insurgency, fear the constitution, among other things, will hand most of the country's oil resources and wealth to Shi'ites and Kurds.
Late Tuesday, Shi'ite and Kurdish leaders agreed to several amendments to the charter, designed to win Sunni support in Saturday's vote. The deal was accepted by one of the largest Sunni Arab political organizations, the Iraqi Islamic Party, who said that it wanted to use the political process to fight terrorism and promote stability.
But other Sunni groups remain deeply opposed. On Friday, a roadside bomb exploded just outside an Iraqi Islamic Party office in central Baghdad, two days after an Iraqi insurgent group threatened to kill the leaders of the party for dropping their opposition to the constitution.