WASHINGTON — The Senate Armed Services Committee, which includes two presidential candidates, Senator Clinton and Senator McCain, is now preparing for what could be a dramatic hearing on President Bush’s nomination of his top general in Iraq, David Petraeus, to head the U.S. Central Command, which oversees the entire Middle East.

The panel’s chairman, Senator Levin, a Democrat of Michigan, said he was “hoping to schedule a prompt hearing.”

General Petraeus, who currently is the commander of Multi-National Force-Iraq, is up for the command of the theater that stretches from north Africa to Southwest Asia and incorporates Iraq, Iran, and Afghanistan. Mr. Bush nominated General Petraeus’s former deputy in Iraq, General Raymond Odierno, to take charge of the Iraq command.

The appointments will likely affect the next president and could set up a conflict if the next occupant of the White House is a Democrat. Both Generals Petraeus and Odierno have not only commanded the surge but testified to Congress on its efficacy. General Petraeus has also pushed to halt any further withdrawal of combat brigades from Iraq after July, when the fifth such brigade is scheduled to return home.

Senator Obama, Mrs. Clinton’s rival for the Democratic presidential nomination, has pledged to begin the withdrawal upon taking office at a pace of one to two brigades a month. Mrs. Clinton has also promised to begin ending the war upon taking office. Both lawmakers have also said that they would take the considered advice of military commanders in the field.

The Senate majority leader, Harold Reid, a Democrat of Nevada, is promising tough questions from his party for the generals. “Our ground forces’ readiness and the battles in Afghanistan and against al Qaeda in Pakistan have suffered as a result of the current costly Iraq strategy. These challenges will require fresh, independent and creative thinking and, if directed to by a new President, a commitment to implementing major changes in strategy,” Mr. Reid said in a statement. He continued: “The Senate will carefully examine these nominations and I will be looking for credible assurances of a strong commitment to implementing a more effective national security strategy.”

Mrs. Clinton praised General Petraeus but noted that he will face a “responsibility broader than Iraq.” She added, “It will be critical that he take a wide view of the serious challenges facing the Central Command area of operations, including the threat posed by Al Qaeda and the Taliban in Afghanistan.”

A senior fellow at the Brookings Institution, Michael O’Hanlon, said that he did not expect Democrats in the end would block the nominations. “If I had to guess today, I would say the vote will be 85 to 15 or 90 to 10.” Mr. O’Hanlon, who had been advising Mrs. Clinton until he removed himself from the campaign after coming under fire from left-wing bloggers for writing positively about the surge, said that Democrats in part could see the appointment of General Petraeus to Central Command as a blessing in disguise.

“There may be people on the left who will enjoy the irony that Petraeus will have to be responsible for Afghanistan,” he said. One of the main arguments from mainstream Democrats is that the war in Iraq is draining resources and troops from the fight in Afghanistan. As the commander at Central Command, General Petraeus will have to be responsible for both.

A scholar at the center-left Center for American Progress, Brian Katulis, said he did not expect Democrats would end up blocking the nominations. “One of the core Democratic arguments is that the Iraq war undermines the fight in Afghanistan. Now you have one of the most effective communicators in the military to convey or talk about the challenges on multiple fronts,” Mr. Katulis said. “It may benefit McCain in the election season.”

Mr. Katulis added that the reshuffle “has serious implications for the next administration.” He added that the combination of General Petraeus, who has favored what Mr. Katulis called a “Iraq-centric policy,” along with at least an interim agreement on the American troop presence signed with the Iraqi government, will put pressure on Democrats to drop demands for beginning a full military withdrawal.

Nonetheless, Mr. Katulis stressed, “It does not make it impossible for a new administration to come in with a different perspective, with a new defense secretary with a new commander in chief, a new secretary of state who has a different strategic assessment of the challenges and a different strategy.” Mr. Katulis praised General Petraeus as a “professional,” and said he has demonstrated that he understands the chain of command.

Mr. McCain yesterday released a statement praising the nominations. The McCain campaign’s director of foreign policy and national security, Randy Scheunemann, yesterday told The New York Sun that both candidates for the Democratic party presidential nomination “have made clear they are going to be utterly irresponsible and ignore military advice and events on the ground in their determination to retreat from Iraq.”

Neither Democratic candidate yesterday said how they would vote. “We would certainly hope Senators Obama and Clinton would welcome the nomination of these two exceptionally well-qualified individuals,” Mr. Scheunemann said.