It was the Tampa motorcade which prompted JFK to order the SS off the
back of the limo.
As Jerry Blaine explained in The Kennedy Detail:
00:35:37 THE PRESIDENT ARRIVED at MacDill air force base in Tampa,
and he helicoptered out to Lopez stadium, and he gave his
speech there.
00:35:48 Then we started a motorcade.
00:35:50 The problem was we had 28 miles of motorcade.
00:35:56 I said, "those guys are gonna be worn out, "so I think I'm
gonna have them
"ride on the back end of the president's car,
"because we just don't have the manpower " all of a sudden,
I hear over the radio, the president wants the ivy league
charlatans to fall
back to the follow-up car, and he politely told everybody,
"we're starting the campaign now, " he said,
"I couldn't get elected dog catcher "
we all of a sudden understood,
but it left a firm command to stay off the back of the car.