NATO leaders gathering in Washington starting Tuesday plan to shore up transatlantic support for Ukraine in its battle against Russia. But for host President Joe Biden, the summit has become just as much about demonstrating he is capable of meeting the grinding demands of the presidency for four more years.

Heads of state from Europe and North America are confronting the prospect of the return of NATO skeptic Donald Trump as Biden tries to save his reelection campaign, which has been in a tailspin following a stumbling June 27 debate performance against Trump.