Leon Hadar draws attention to the GOP’s postwar history as the party of hawkish nationalism:

Indeed, as scholar Colin Dueck proposes in his Hard Line: The Republican Party and US Foreign Policy Since World War II Republican and conservative foreign policy post-World War II was very hawkish and nationalist in contrast with the earlier more anti-interventionist approach of Republican Robert Taft.

John Lukacs has observed several times that the Republican Party is the more nationalist of the two major parties in the United States. During most of the Cold War and in the immediate aftermath of 9/11, this worked to the party’s political advantage on matters of national security and foreign policy. When the public perceived security threats to be genuine, the more nationalist party often receives the benefit of the doubt on these issues, and a relatively more hard-line approach to those threats is rewarded politically. However, in the absence of a significant foreign threat or in the wake of repeated exaggerations and misrepresentations of the nature of foreign threats, the more nationalist party is at a near-constant disadvantage because it ceases to appear as the responsibly “tough” party and comes to be seen as the recklessly belligerent one.

The party’s positions may or may not have changed that much in the interim, but at some point the public no longer sees hard-line policies as reassuring and necessary and begins to view them as destabilizing and foolish. One reason for this change in attitude is that the public may see the results of hard-line policies and they conclude that they were wrong to support them. Another reason may be that the hard-liners in the more nationalist party react to failure by becoming even more unreasonable, which has the effect of alienating people otherwise inclined to support the party. That is the current situation for the GOP, and the only available remedy to it that I see is to re-orient itself away from hard-line policies in order to adapt for an era of relatively small and limited security threats. The world has become much safer for the United States, and that needs to be reflected in Republican foreign policy thinking.