U.S. President Joe Biden managed to reassure NATO leaders about his fitness for office with a strong speech at the opening of the alliance’s 75th anniversary summit, but it wasn’t enough to quiet growing doubts about his chance of winning reelection in November.

Delegations from across Europe were quietly slotting in meetings with advisers and others with links to former U.S. President Donald Trump as they grapple with the possibility — some say likelihood — that he will reclaim the Oval Office. They were hoping to get a clearer sense of just what a Trump victory might mean for an alliance he regularly targets for criticism.

European officials who expressed confidence about Biden’s reelection hopes as recently as this spring were more downbeat in private conversations this week. Some sought to look on the bright side, arguing that Trump would be hard-pressed to follow through on his threats to undermine security guarantees for NATO members or push Ukraine into a hasty peace deal with Vladimir Putin.