MUNICH — There was a lot for diplomats and policymakers to consider when they gathered at a recent global security conference in Munich: China rising, Russia meddling, Germany weakening. But the inescapable question — the one that might change the world most immediately for Europe — was whether President Trump would win re-election in November.

Rightly or wrongly, the consensus among European diplomats and analysts is that Mr. Trump is likely to get a second term. But there was also consensus that such an event would be a significant part of a drastic, and potentially permanent, shift in global affairs for which Europe remains woefully unprepared.

Mr. Trump’s re-election would represent a fundamental change, said François Heisbourg, a French analyst. “Eight years in political terms is an era, not an error. And it would undermine the reality of American democracy.”

Secretary of State Mike Pompeo’s admonishment to the Europeans to accept American leadership and “reality” was met at the conference with stony silence. Traditional American allies were far from assured that they would be able to depend on the United States in another Trump term.