Mark Leonard is co-founder and director of the European Council on Foreign Relations, the first pan-European think tank.

John McCain may have called Barack Obama the biggest celebrity in the world, but the place that has held the U.S. president closest to its collective heart has always been Europe. When he took to the stage in Berlin on July 24, 2008, a crowd of 200,000 Germans abandoned their usual reserve to flood screaming and cheering into the Tiergarten.

They came to see an aspiring American president give flesh to all of Europe's fantasies about American leadership: multiethnic and multilateral; pragmatic and peacefully minded; social democratic in his goals and so eloquent in their expression. Obama promised to purge the sins of George W. Bush and give new impetus to the alliance for a new century. "America has no better partner than Europe" he said.

The paradox is that while Obama successfully healed the transatlantic rift, he may also be the American president who presided over the end of the West as a political community.

Four years on from Berlin, Obama would still trade his approval ratings in any European country with those in his native United States. In June, the Pew Global Attitudes Survey showed that nine out of 10 voters in France (92 percent) and Germany (89 percent) would like to see him reelected, as would large majorities in Britain (73 percent), Spain (71 percent), Italy (69 percent) and the Czech Republic (67 percent). And at a tactical level, Europeans and Americans are cooperating more closely -- on a range of issues from Iran to Syria -- than they have for many years. Even when they disagree, they do so with civility and a surprising absence of rancor.

But Obama's stellar personal ratings in Europe hide the fact that the Western alliance has never loomed smaller in the imagination of policymakers on either side of the Atlantic...