This thesis examined whether party identity (ID), or the ideological score assigned by Americans for Democratic Action (ADA), was a better predictor of roll-call voting on Iraq War legislation during the 110th Congress in 2007. Party ID and ADA scores were separately correlated with voting outcomes on twenty-two Senate, and twenty-six House votes on Iraq War bills. Though party and ideology both correlated strongly with voting outcomes in cross-tabulation statistics, a test of significance of the difference between two nonindependent correlations revealed ADA scores predominated in all House votes, and nearly half of the Senate votes. While the results add evidence of the increasing ideological homogeneity of parties, the particular attitudes toward military intervention directly challenged by Iraq War policy, and the mixed influence of party and ideology across Senate voting, suggest that prospects for bipartisanship in future intervention issues would depend on the justifications and circumstances of the policy.