Which of the Following Events Is an Example of the "Bandwagon

Which of the following events is an example of the "bandwagon effect"?

A) An incumbent candidate loses a political debate,but earns his party's nomination regardless.
B) Unable to decide between two strong candidates,a party compromises to nominate a little-known candidate.
C) Commentators proclaim a political debate a tie,but the lesser-known candidate receives a favorable bump in the polls.
D) Commentators proclaim a candidate the winner of a political debate; the candidate then carries that momentum to gain his party's nomination.