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