The Candidate is a movie about a little guy running against big time politicians and the big time political establishment in the Democratic Party. He's Bill MacKay, played by Robert Redford, running against his own party and against Mr. Establishment, U.S. Senator Crocker Jarman played by Don Porter. McKay's campaign manager played by Peter Boyle is part of that Democratic establishment but wants to run an outsiders campaign without allowing the outsider MacKay to get too far out in left field. You see these two men fighting against each other in the campaign.
The outsider Bill MacKay runs his campaign based on his beliefs. He gives voters a good idea of who he is and speaks his mind. He probably doesn't use a speechwriter for the whole campaign. His opponent, three-term incumbent U.S. Senator Crocker Jarman just tries to be likable expressing traditional America values, speaking mostly to older voters. He says you should reelect me because I stand up for America etc.