In that Democratic primary McCarthy was challenging the incumbent President Johnson for the nomination, a long shot as seen by most. But the Vietnam War was taking its toll on Johnson—and McCarthy was running as a peace candidate (notice the doves of peace swarming around our fair knight). McCarthy DID survive, doing quite well, and was ready to move on.
Less than 2 weeks after this strip saw print, President Johnson stunningly announced that he would not seek the nomination. I remember exactly where I was, as a kid, when I listened to that live radio speech, when Johnson started out with that "Muh fellow Amuricans...Uh come to you tonight with a heavy heart..."
And the way was clear for McCarthy, oh but for that other shining knight, Bobby Kennedy.