It would be easy to call President Trump’s Sunday rally at Madison Square Garden an instance of the medium, or perhaps venue, being the message — bright lights and a big crowd galvanized by the promise of restoring America’s greatness. Beyond the theatrical aspects, however, came a lashing of the Democratic Party leveled by a former member of it, Robert F. Kennedy Jr.

For the onetime independent presidential candidate, who joined Mr. Trump’s transition team in August, today’s radicalized Democratic Party “is not the party anymore of Martin Luther King, of Robert Kennedy, of John Kennedy.”