Competition fuels party conflict by raising the political stakes of every policy dispute. When control of national institutions hangs in the balance, no party wants to grant political legitimacy to its opposition by voting for the measures it champions. After all, how can a party wage an effective campaign after supporting or collaborating with its opposition on public policy? Instead, parties in a competitive environment will want to amplify the differences voters perceive between themselves and their opposition. They will continually strive to give voters an answer to the key question: “Why should you support us instead of them?” Even when the parties do not disagree in substantive terms, they still have political motivations to actively seek and find reasons to oppose one another. In an environment as closely competitive as the present, even small political advantages can be decisive in winning or losing institutional majorities.
During the long years of Democratic dominance following the New Deal, politics was less contentious in part because the national political stakes were so much lower. Democrats did not perceive themselves in danger of losing their outsized majorities. The “permanent minority” Republicans did not see a path to majority status. In such an environment, members of the minority party were more willing to bargain over legislative initiatives in which they would vote “yea” in exchange for substantive policy concessions, because such support did not grant political legitimacy to an opposition that they hoped to vanquish at the next election. Meanwhile, members of the majority party were more willing to fight about public policies internally among themselves, rather than attempting to close ranks against an opponent that had little perceived chance of winning power.