Okay kiddo, so there was this man named Jack Kennedy who was the President of the United States many years ago. He was very popular and people loved him a lot.
Then, there was a man who wanted to be the President too, and his name was Lloyd Bentsen. He was in a debate with another man who wanted to be Vice President next to the President.
During the debate, the other man said something that he thought was clever and funny. He said, "I knew Jack Kennedy, and you, sir, are no Jack Kennedy."
Now, this was kind of mean because he was trying to say that the other man wasn't as good or as popular as Jack Kennedy.
But then, Lloyd Bentsen very strongly replied, "Senator, you're no Jack Kennedy." He was saying that the man wasn't like Jack Kennedy at all and shouldn't compare himself to such a great leader.
It was a big moment in the debate and made the man who compared himself to Jack Kennedy look kind of silly.