People
I think this is the most extraordinary collection of talent, of human knowledge, that has ever been gathered together at the White House--with the possible exception of when Thomas Jefferson dined here alone.
— John F. Kennedy

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker praises a gathering as the most extraordinary display of talent and knowledge ever assembled in that house, then adds a twist. The exception is Thomas Jefferson dining alone, which flatters the guests while also paying a witty tribute to one exceptional man.
Context reviewed