But by the late 1990s, during America’s post-cold-war triumphalist moment, Senator McCain gradually but decisively moved away from his realist roots and became an enthusiastic champion of an ideological interventionist agenda. To be fair, many in the political center, including key Republican realists, came to believe that, as the only superpower, the United States was both able and entitled to reshape the world without paying a prohibitive price. ~The National Interest

McCain’s move from hawkish realism, which prompted him to criticize deployments to Lebanon and Somalia, to super-hawkish interventionism can be overstated, but it is clear that during the Balkan Wars McCain abandoned any hint of realism.  Complicating matters, McCain was correct in his arguments against intervening in Lebanon and Somalia, which sounded eerily similar to many conservative arguments against invading Iraq.  At one time, he was wary of intervention because of the intractability of local conflicts, our lack of understanding of the divisions in a very different foreign society, and the lack of clear objectives and direct connection to the national interest, but cast all of that aside to support intervention in the Balkans of all places.  Since then, there has never been a major deployment or use of force that he has opposed.  No one denies that there has been a shift in his views, but as far as I know what no one seems to be able to account for is why, aside from opportunism or perceived political advantage, he came to side with the very kinds of people who would not only have wanted to go into Lebanon and Somalia but who also regularly decry the subsequent withdrawals from those places as invitations to attack.