Richard Nixon targeted John Kerry for his anti-war activities. From a long MSNBC piece on what the Nixon White House (via the infamous tapes) had to say about Kerry:
Colson: This fellow Kerry that they had on last week —
Colson: — hell, he turns out to be, uh, really quite a phony.
Nixon: Well, he is sort of a phony, isn’t he?
Colson: Well, he stayed, when he was here —
Nixon: Stayed out in Georgetown, yeah. 
Colson: — was out at the best restaurants every night and, uh —
Colson: — you know, he’s just, the complete opportunist.
Nixon: A racket, sure. 
Colson: We’ll keep hitting him, Mr. President.I can see the headline now… Kerry says he was the inspiration for
Love Story Watergate.