Sen. John McCain (Ariz.) is the top Republican on the Senate Armed Services Committee, which will hear testimony from Petraeus on April 8. Sen. Hillary Rodham Clinton (N.Y.) is one of the Democrats on the panel, which will also hear from U.S. Ambassador to Iraq Ryan Crocker.

The Armed Services Committee hearing could serve as a platform for McCain and Obama to highlight their differences over Iraq with an eye toward a possible November match-up. Clinton, who voted for war authorization, has promised to bring home the troops soon after she takes office while McCain has vowed to remain in Iraq until the war is won.

Iraq also has been a contentious issue between Clinton and Obama, who has criticized Clinton for authorizing the war. Both Democrats have criticized McCain for his support of the war.

At the same time, the testimony by Petraeus, who Clinton has praised on the campaign trail, could put Clinton and Obama in a complicated position, according to Michael O’Hanlon, a senior fellow at the Brookings Institution.

He said the two Democrats may want to avoid directly criticizing Petraeus for his recommendations. They also may not want to focus on the implications of a quick drawdown, he said.

Instead, O’Hanlon said they will lob their criticism at failures in the Iraqi political system.

McCain, who opposes withdrawing troops from Iraq, could be boosted by the Petraeus appearance. O’Hanlon said he would probably seek to ask questions about what it would mean to quickly withdraw most U.S. troops from Iraq.

The Petraeus review comes at a time when violence is flaring in the southern Iraqi city of Basra, where Iraqi security forces have had a hard time taking over combat and policing duties from the U.S. troops. Iraqi government troops have also battled in recent days with Shiite militias in Baghdad.

Whoever wins the presidency in November could inherit as many as 140,000 troops still deployed in Iraq. That’s about the same number as before the so-called surge of 35,000 troops announced in January 2007.

President Bush has said he will not decide whether to further withdraw troops until after Petraeus’s and Crocker’s testimony in the Senate and the House. Petraeus has already advised against withdrawing more troops than those added last year during the surge.

Democrats have been less eager to talk about Iraq than they were last year, but some are starting to criticize the administration for signaling it will not continue to withdraw troops after July.

“In fact it appears there will be as many if not more U.S. troops in Iraq at the end of the year than there were before the surge began in 2007 and in that time the president’s policies have not resulted in the political reconciliation needed for a long-term solution to the conflict in Iraq,” Senate Majority Leader Harry Reid (D-Nev.) said in a statement Thursday.

The Democratic leadership will also have to figure out a strategy on how to provide war funding for the rest of this year. Congress approved only $70 billion for 2008 war operations at the end of last year, and the Pentagon has more than $100 billion remaining in its request for this year.

The Pentagon leadership, including Defense Secretary Robert Gates, has urged Congress to approve the rest of the supplemental this spring to avoid disruptions in Pentagon operations outside the wars in Iraq and Afghanistan. The Pentagon’s current war funding would be exhausted by July.