WASHINGTON — President Joe Biden nounced  Sunday that he will end his presidential re-election campaign, bringing an abrupt and humbling conclusion to his half-century-long political career and scrambling the race for the White House just four months before Election Day.

Biden, 81, could not reverse growing sentiment within his party that he was too frail to serve and destined to lose to Donald Trump in November. He backed Vice President Kamala Harris to replace him as the Democratic nominee.