Mr. Rubio is challenging the strain of isolationism emanating from some grass-roots conservatives and building a reputation as an internationalist willing to deploy American power – he has advocated greater American support for the anti-Assad forces in Syria, criticized President Obama for not sustaining a sufficient American commitment in Libya and suggested that the only way to stop Iran from acquiring nuclear weapons might be military action. …

Mr. Paul eschews the isolationist label attached to him by his association with his father, former Representative Ron Paul of Texas, whose antiwar, inward-turning stances defined his national reputation. But Senator Paul nonetheless reflects the deep suspicion about global entanglements evident among libertarians and some Tea Party adherents, and in some ways is a perfect foil for Mr. Rubio’s efforts to position himself as a moderate, mainstream leader of a new generation of Republican leaders on foreign policy. …

Both are grappling with how to reconcile the aggressiveness of the neoconservatives, the fervor of the evangelicals, the warnings of overextension by fiscal conservatives and the efforts by traditional Republican “realists” to impose a more pragmatic, less ideological lens onto the party’s approach. And with seats on the Foreign Relations Committee alongside advocates of assertive American foreign policy like Senator John McCain of Arizona, they have a platform to air their views, as they did this week in hearings on the security failures that led to the deaths of Americans at the diplomatic mission in Benghazi, Libya, and on the nomination of Senator John Kerry to be secretary of state.