Final answer:
The party in power usually loses seats during midterm elections because of the reverse-coattail effect but may gain during presidential elections through the coattail effect. When no majority is won, parties form coalitions.
Step-by-step explanation:
The party in power typically loses seats in Congress during midterm elections due to a phenomenon known as the reverse-coattail effect. This occurs as the electorate often holds the president's party accountable for their actions or inaction. On the other hand, during a presidential election year, the party in power might gain seats if the presidential candidate is popular, benefiting from the coattail effect. Therefore, the correct answer is b) The party in power typically loses seats due to decreased voter support. Additionally, when no party wins a majority in the legislature, parties often form coalition governments, which can be fragile as they depend on the continued cooperation of the coalition members.