Those events will make 2009 a watershed year in Iraq - perhaps the most significant since the U.S.-led invasion nearly six years ago.
If things go well, Iraq could be on its way to relative stability - if not the liberal, Western-style democracy foreseen when the U.S. led the 2003 invasion to oust Saddam Hussein.
But failure could lead to a new spiral of violence. The risk of failure is high.
The suspicion and bitterness among Shiites, Sunnis and Kurds that fueled the conflict still run deep, even though attacks have fallen by 80 percent since last March, according to the U.S. military.
Iraq remains a shattered country, where millions lack security, clean drinking water, jobs, electricity - and hope.
Nevertheless, Iraq's prospects may be better than at any time since the war began.
In 2008, U.S. and Iraqi forces gained the upper hand in the fight against Sunni and Shiite militants, reducing violence in Baghdad and other cities to levels not seen in five years. The U.S. military mission is already more peacekeeping than fighting a war.
The coming year will tell whether the Iraqis can build a political system in which the different religious and ethnic groups feel power is shared fairly.
Regional elections Jan. 31 in 14 of Iraq's 18 provinces, and nationwide parliamentary balloting by the end of 2009, offer Iraqis a chance to select leaders they believe represent their interests.
Most Sunnis and many Shiites boycotted the last regional elections in January 2005. Many Iraqis also believe the national parliament chosen later that year no longer represents their interests, and they are eager for change.
Much will depend on how the new U.S. administration manages the draw-down of its 150,000-strong military force here. President-elect Barack Obama wants to shift resources to Afghanistan and the economic crisis at home.
Under the newly approved U.S.-Iraq security pact, all U.S. troops must pull out of Iraqi cities by the end of June and leave the country entirely by the end of 2011. Already, the Pentagon plans to send home about 8,000 troops by February.
Obama wants all combat troops out of Iraq by the spring of 2010, leaving a residual force of trainers, air controllers, advisers and logistics soldiers until the end of the mission.
The incoming president, however, has promised to consult his commanders and the Iraqi government before ordering withdrawals.
Britain plans to remove the last of its 4,000 soldiers by June.
U.S. commanders and some analysts worry that a quick departure could trigger more violence because Iraqi security forces may not be ready to take on more responsibility.
"Our really crucial role is to act as peacekeepers to police an uneasy cease-fire," said Stephen Biddle of the Council on Foreign Relations. "Iraqis do not yet trust one another enough for indigenous Iraqi security forces to stabilize such a fearful country."
Publicly, U.S. officials speak in glowing terms about improvements in the Iraqi security forces. Privately, some senior military officers doubt the Iraqis will be ready to fight on their own by the time the U.S. leaves in 2011.
U.S. and Iraqi officials have highlighted the Iraqi army's success in rousting Shiite militants from Basra and Baghdad's Sadr City district last spring.
But success came only after mutinies in Iraqi ranks, and needed strong U.S. logistical and air support plus political intervention by Iran, which helped mediate a cease-fire in Basra.
Less has been said about the Iraqi army's performance in the northern city of Mosul, where U.S. and Iraqi forces are struggling to curb Sunni militants, including al Qaeda in Iraq.
"Iraq and the U.S. are reaping some of the consequences of past reports that exaggerated the progress in developing the Iraqi security forces," former Pentagon analyst Anthony Cordesman wrote in a recent study.
Cordesman, a frequent visitor to Iraq, said many U.S. and Iraqi politicians have taken "exaggerated reporting too seriously" and need to understand how far the Iraqis "still have to go."
Major tests will come around the two elections, when U.S. commanders believe insurgents will accelerate attacks to try to disrupt the campaign. Some Iraqi politicians worry that the government will use the police to intimidate opposition candidates.
Ahead of the voting, old political alliances are already fraying. Both Sunni and Shiite parties face major challenges to their claim of leadership of their two religious communities.
Prime Minister Nouri al-Maliki's party is trying to win over followers of radical Shiite cleric Muqtada al-Sadr. His position has weakened since his Mahdi Army militia lost its bases in Baghdad's Sadr City and Basra in fighting last spring.
Al-Maliki has complained that the autonomy enjoyed by his Kurdish partners since 1991 has weakened the central government. He has called for amendments to the constitution - something that alarms the Kurds.
Sunnis who turned against al Qaeda fear the Shiite-led government will forget its promises to give them jobs in the government or the security forces.
Biddle believes there is still a "serious danger" that major violence could return "if we and the Iraqis fail to follow the necessary policies."
"If we do this, I think there's an important opportunity for sustainable stability," he said. "If we don't, then I think we take a grave risk of losing what has been gained."
Robert H. Reid