I think George H.W. Bush was confronted with some huge challenges - the invasion of Kuwait, the fall of the Berlin Wall, the fall of the Soviet Union - that he managed with great aplomb.
Anybody who has been to Chicago has a very positive view. But not everybody has come to Chicago, and in many ways, Chicago is an undiscovered treasure. It punches below its weight internationally.
Putin wants nothing less than to return Russia to the center of global politics by challenging the primacy that the United States has enjoyed since the end of the Cold War.
Many observers believe that the greatest damage Russia has done to U.S. interests in recent years stems from the Kremlin's interference in the 2016 U.S. presidential race. Although there is no question that Moscow's meddling in American elections is deeply worrying, it is just one aspect of the threat Russia poses.
President Trump is hardly the first U.S. president to call on the European allies to do more - in one form or another, every president since Harry Truman has done so. What is different this time, however, is Trump's suggestion that America's commitment to the alliance is conditional.