Commander-in-chief in waiting? Hillary Clinton is optimistic about America’s ability to defend its interests abroad ©Justin Sullivan/Getty Images

When Hillary Clinton eviscerated Donald Trump in a speech in June, she did so on the grounds that he was hopelessly unprepared and temperamentally unsuited to be commander-in-chief. She derided the foreign-policy positions of her Republican rival for the presidency as a farrago of contradictions and provocations—“not even really ideas,” she said, “just a series of bizarre rants, personal feuds, and outright lies.”

What Clinton didn’t do was to lay out her own foreign-policy agenda. Her implication was that Trump was so manifestly unqualified for the Oval Office that her prescriptions for how to end the civil war in Syria or counter the predations of Vladimir Putin in Ukraine were almost beside the point. The reaction from the cheering crowd in San Diego, California suggested that Clinton was right: she didn’t yet need to offer a lengthy list of policy alternatives to Trump. Her record—as First Lady to President Bill Clinton, Senator from New York, and above all, as President Barack Obama’s secretary of state—spoke for itself.

Still, as American voters pivot this summer from the primaries to the general election, Clinton’s foreign policy will come under greater scrutiny. When it does, people might be surprised by the extent to which she parts company with her former boss. A fervent believer in the concept of “American exceptionalism,” Clinton is more open than Obama to the calculated use of military force to defend national interests. She is more optimistic than he is about American intervention, believing that it does more good than harm. She believes the writ of the United States properly reaches, as George W Bush once declared, into “any dark corner of the world.”

Clinton and Obama, one could argue, have come to embody competing visions of America’s role in the world: his vision is restrained, inward-looking, radical in its acknowledgment of limits; hers is hard-edged, pragmatic, unabashedly old fashioned.

Those long-held principles will also put her at odds with Donald Trump. If one picks through the bluster and contradictions in his statements, there are some clear warnings. He has threatened to withdraw American support for NATO, pull the US nuclear security umbrella…

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