Are America’s leading presidential candidates up to it?

One, from a star-studded fund-raiser held in Los Angeles on June 15th, shows Mr Biden staring blankly at the audience before Barack Obama, the night’s other headline act, grasps his arm and leads him offstage. The second, taken a few days earlier at the G7 summit in Italy, appears to show Mr Biden wandering away from other world leaders as they watch a skydiving demonstration. In conservative corners of the media and the internet, such clips of Biden freezes abound. Another recent entry shows the president staring blankly at a White House concert celebrating the new federal holiday of Juneteenth on June 19th, which marks the end of slavery.