In the West Wing (Manchester Part II) we see Jed say about his running for the Presidency:
BARTLET: I got in it polling in the single digits. Hoynes had it locked up. I got in it to give some speeches and keep him honest...
In the West Wing (Red Mass) we see Stackhouse (running as a third party candidate for the President) say:
STACKHOUSE: I got in it to raise issues.
My question is: What is the evidence that a secondary party primaries candidate can influence the rhetoric of the leader?