And Petraeus is experienced in making his case. Over the last year he has assiduously courted other military officers, academics and congressional delegations, proving remarkably successful at converting his skeptics.
But in Washington, during a campaign season, the partisan lines for and against the war have hardened. Some analysts sympathetic to Petraeus believe that by scaling back his ambitions -- acknowledging that Iraq is unlikely to become a "Jeffersonian democracy" any time in the next decade, for instance -- Petraeus may convince Democratic contenders that achievable goals warrant a continuing presence in the country.
"The right near-to-midterm objective is an end to widespread violence -- get a nationwide cease-fire," said Stephen D. Biddle, a scholar at the Council on Foreign Relations who has advised Petraeus' staff. "That is plausible; that is achievable. . . . And it sounds a lot more realistic to people than the kinds of things the president has said."
Not all of the questioning from the presidential candidates is expected to be hostile. McCain, the senior Republican on the Senate Armed Services Committee, will align himself with Petraeus' strategy to keep troop levels at 140,000 through the summer, aides said.
"He believes, like the theater commander does, that to draw down beyond that at this point would be dangerous and threaten some of the gains that we made," said McCain campaign strategist Mark Salter.
But it is the potential clash with the Democrats that will be most closely watched by political and military Washington.
Inside the Pentagon, a contingent of senior officers -- including members of the Joint Chiefs of Staff -- has long pushed for a faster drawdown of forces to relieve stress on the Army and to meet needs elsewhere, particularly in Afghanistan.
Some senior officers have privately complained about Petraeus' direct access to President Bush, noting that under law the chairman of the Joint Chiefs of Staff is the primary military advisor to the president.
Late last year, there was even a move among some senior military officers within the Pentagon to reshape Petraeus' role during this month's congressional hearings, relegating his voice to just one of many heard by lawmakers.
Pentagon officers wanted to emphasize potentially competing views, particularly from Petraeus' immediate superior at the time, Navy Adm. William J. Fallon, commander of U.S. forces in the Middle East. Fallon was forced to resign last month over differences with the White House. He has privately advocated a speedier drawdown in Iraq.
