WATCH: Confused Biden Introduces Ukraine's Zelensky as 'President Putin'

Gaffe came shortly before octogenarian leader's highly anticipated press conference

WATCH: Ruben Gallego, Running for Senate in Migrant-Flooded Arizona, Says Border Issues Aren't His 'Expertise'

Gallego's admission comes as polls show the border is a top issue for Arizona voters

WATCH: Karine Jean-Pierre Dodges on Whether Biden's Team Would Wake Him If America Were Nuked

'Could Have Diagnosed Him From Across the Mall': Democratic Neurosurgeon Tells NBC Biden Clearly has Parkinson's

WATCH: Babbling Biden Lashes Out at Critics During MSNBC Phone Interview

WATCH: Joe Biden's Senior Moment of the Week (Vol. 101)

'You got to know how to know'

WATCH: Joe Biden Recites His ABCs (Vol. 3)

'Say hello to oyster bunnies!'

WATCH: Watergate Reporter Says Biden Had 15-20 ‘Horror Show’ Episodes in Past Year

Carl Bernstein said Biden's dismal debate performance was not a "one-off"

WATCH: Joe Biden's Senior Moment of the Week (Special Debate Edition)

'We finally beat Medicare'

CNN's Van Jones Eulogizes Joe Biden