[cnn-photo-caption image= http://i.l.cnn.net/cnn/2008/POLITICS/04/07/iraq.candidates/art.petraeus.ap.jpg caption=" Army Gen. David Petraeus was expected to face several tough questions about Iraq on Tuesday."]WASHINGTON (CNN) - The emotional debate over the war will once again dominate presidential politics when all three candidates have opportunities to question the top U.S. general in Iraq during congressional hearings Tuesday.
Sen. John McCain, the presumptive GOP presidential nominee, and Sens. Hillary Clinton and Barack Obama, the two rivals for the Democratic nomination, will share the spotlight when Army Gen. David Petraeus and Ambassador Ryan Crocker, the top U.S. diplomat in Iraq, testify.
McCain and Clinton will question Petraeus and Crocker - and possibly advocate their positions on whether U.S. troops should be withdrawn - when they appear before the Senate Armed Services Committee on Tuesday morning. McCain is the committee's top Republican.