John Dickinson : I trust, Caesar, when you're through converting the poor fellow to independency, you'll give the opposition a fair crack at him.
Caesar Rodney : [chuckling] You're too late, John. Once I get 'em, they're got.
(In fact I saw them in a video, though they are the same with the linked text.)
What do the parts in bold mean?
I am having a hard in figuring them out.
Many thanks in advance.