Final answer:
Party polarization is the increasing divergence and ideological differences between political parties. It affects a moderate candidate's ability to win elections because they may struggle to appeal to the increasingly polarized base of the party and face competition from more extreme candidates.
Step-by-step explanation:
Party polarization refers to the increasing divergence and ideological differences between political parties. It is the result of moderates leaving the parties, causing the parties to become more ideologically extreme and dissimilar. This has implications for moderate candidates' ability to win elections because they may struggle to appeal to the increasingly polarized base of the party and face competition from more extreme candidates.