For decades, Americans have trusted the Republicans over the Democrats to handle national security issues, by a wide margin. Over the Bush presidency, that gap has disappeared. The authors explore the causes and consequences of this loss and suggest several new avenues for research on issue ownership. Findings indicate that Bush's handling of the Iraq war has played a decisive role in diminishing the Republican Party's reputational advantage on national security. This has had significant electoral repercussions both for the president and his copartisans in Congress.