Activists opposing Donald Trump gathered outside the White House on Sunday on the U.S. president's 74th birthday. As Trump turned 74, an incident a day earlier in which he appeared unsteady on his feet revived questions about his health as he heads into a grueling re-election campaign.

Scrutiny of the president's health has always been intense, and Trump has generally appeared vigorous for his age. Results of a routine physical released earlier this month showed that he was overweight, but with otherwise normal results. But his appearance at the U.S. Military Academy at West Point raised new questions about apparent signs of unsteadiness, balance problems and trouble enunciating certain words.