Key Democrat and Republican lawmakers are looking ahead to Thursday's election in Iraq, saying Iraqis need to move toward political compromise and unity even as they continue to fight the insurgency with the help of the United States.

Among observers of Thursday's election will be three U.S. Senators, including Joseph Biden, the top Democrat on the Senate Foreign Relations Committee.

He will join Republican Senators Lindsey Graham and Saxby Chambliss, and possibly one other Democrat, visiting Iraqi polling stations, observing voting, and meeting with U.S. troops and commanders.

Addressing reporters Tuesday, Senator Biden said a key to success will be a strong turnout, in particular by Sunni voters. "I hope and I expect there will be a significant turnout in all communities, including [by] Sunnis. I think they learned their lesson from the last election that sitting out is against their interests and I expect there will be a significant Sunni turnout," he said.

Even with a strong turnout, Senator Biden says it will be up to Iraq's new parliament to take what he believes is the absolutely necessary step of amending the constitution to overcome differences that might lay the groundwork for future problems.

If the constitution proves to be a divisive document rather than a uniting one, Senator Biden adds, the chances of civil war in Iraq will increase.

Earlier Tuesday Senate Republican Majority Leader Bill Frist addressed some of the same themes: "Iraq's Sunni Arabs are coming to recognize the importance of taking part in that democratic process. Only through peaceful politics can the Sunni Arab community in Iraq ensure that its rights are secured, its interests protected, and its people represented at the national, provincial and local levels," he said.

Key Republican Senators went to the White House Tuesday, meeting with President Bush and his National Security Adviser Stephen Hadley about the upcoming election.

On Wednesday, President Bush delivers the last of four speeches about progress, as well as challenges in Iraq.

And he is sending Secretary of State Condoleezza Rice to Capitol Hill to brief lawmakers in advance of the Iraqi election.

Senator Russ Feingold, a key Democratic critic who is considering a run for the White House in 2008, used a speech on the Senate floor Tuesday to urge what he called a flexible timeline and clear benchmarks for withdrawing troops from Iraq. "The current massive U.S. military presence, without a clear strategy and a flexible timetable to finish the military mission in Iraq, is actually fueling the insurgency and will ultimately prevent the very economic and political progress that the Iraqis are demanding, and that the president has started to talk about in his speeches," he said.

General Mark Kimmett, of the U.S. Central Command, said Tuesday while there has been some sectarian violence in Iraq, it is not accurate to describe the situation there as a civil war.

Congressman John Murtha, who has called for U.S. troops to leave within six months, has said he believes a civil war is underway in Iraq, and that American forces are in the middle of it.