Public opinion and congressional majorities do not favor the president’s new Iraq plan, but even expressing clear disapproval, never mind forcing the president to change course, is exceedingly difficult for a cacophonous body of 535.

The ongoing debate over Iraq is rare in that it paints in stark relief two views of our separation-of-powers system. President Bush has been among the strongest defenders of presidential power, exercising wartime powers and making generous use of signing statements to stake out his prerogatives. The new Democratic Congress looks back to the early and mid-’70s, when Congress declared war on an imperial presidency, limiting presidential action in Vietnam, passing the War Powers Act and reining in the activities of intelligence agencies.

Constitutional scholars of various stripes gave a thoughtful exposition of these opposing theories before the Senate Judiciary Committee last week.

But the reality of these clashing views of the executive power in war is that they cannot coexist, and courts are loath to step in to draw clear lines of presidential and congressional authority. In these matters, Congress and the president are left to fight these battles out themselves. And while Congress does have tools it can use to alter presidential actions, it often requires enormous majorities for Congress to act as decisively as the president. The heyday of congressional direction of foreign policy occurred in the Nixon and Ford administrations, when Democrats had between 54 and 61 Senate seats and 242 and 291 House seats.

In the debate over Sen. John Warner’s (R-Va.) and Sen. Carl Levin’s (D-Mich.) resolution of disapproval of the president’s new war strategy, the fractious nature of Congress is on display for all to see.

Senate Republicans have three aims. First, they hope to muddle the message coming out of Congress, with a series of votes on Warner-Levin, on Sen. Judd Gregg’s (R-N.H.) resolution that Congress supports funding the troops, and on a Sen. John McCain (R-Ariz.) resolution that supports the president and provides benchmarks for the Iraqis to meet. Second, Republicans want to allow their potentially vulnerable 2008 candidates an opportunity to voice disagreement with the president. Sens. Norm Coleman (R-Minn.) and Susan Collins (R-Maine) have already sided with Democrats on the cloture vote. Sens. Gordon Smith (R-Ore.) and possibly John Sununu (R-N.H.) will want some vote down the line to indicate their differences with the president. Third, with the Gregg proposal, they hope to put a large number of Democrats on record as supporting funding the troops, making later efforts to limit funding more difficult.

Democrats want a simple vote on Warner-Levin to send a message of bipartisan opposition to the president’s new war strategy. But even passage of the resolution will not appease the anti-war base of the party, which demands much stronger action. The major Democratic presidential candidates are practically tripping over each other to get to the anti-war left of Sen. Hillary Rodham Clinton (D-N.Y.).

All of this sets the stage for phase two of the conflict, when there will be attempts to use war funding to tie the president’s hands. Democrats are not likely to cut off funds directly, but to attach to funding limits on the length of deployment of National Guard troops or other measures that constrain the president’s ability to increase and maintain the level of troops in Iraq. They may succeed, but the president and his allies in the Senate will not make this an easy task.

President Bush may not turn the polls around on Iraq, but it is difficult for a Congress without overwhelming majorities to force his hand in the conduct of war.

Fortier is a research fellow at the American Enterprise Institute.