Parties, from the beginning of the Republic, have been a central force in American politics, clarifying the policy choices available to American voters. They provide the basis for organizing elections and political power in the institutions of government even as they compete constantly for loyalty and fealty with the institutions themselves. Members of Congress loyal to the president’s party sometimes reflexively follow his lead, denying or papering over his failings and failures. At other moments—driven by personal beliefs or constituency interests, by electoral imperatives, and sometimes, at least, by faithfulness to the public interest and the fundamentals of the Constitution—they keep their distance from him. And members of the party opposed to the president often challenge his positions.
But during some periods of divided government, when one party controls the White House and the other has a majority in the House, the Senate, or both chambers, cross-party coalitions where parties share responsibility for governance have thrived. As political scientist David Mayhew showed, divided government during the decades following World War II produced significant legislative achievements—and arguably did so as or more often than when a single party held all the reins of power.Tribalism, which cast members of the opposing party not as worthy adversaries but as dangerous enemies, swept that respect away.>
Strong Democratic majorities in Congress in the 1930s voted for sweeping New Deal legislation—but many Democrats joined with Republicans to block Franklin Roosevelt’s attempt to enlarge the Supreme Court. Republicans in the majority in 1947-48 vigorously opposed most of Harry Truman’s agenda—leading to his famous campaign in 1948 against the “Do-Nothing Republican Congress.” But the same Congress joined with Truman to enact the Marshall Plan, as well as a historic and (to this point, at least) enduring reorganization of the national-security apparatus that created the National Security Council and made it easier to coordinate defense and foreign policies. Most Democrats in the Reagan era opposed his initial plans to slash government and cut taxes, but conservative Democrats provided enough votes for Reagan to enact an early package. Then, in subsequent years, Democrats bargained with him to increase taxes to combat the burgeoning deficit his program produced and to stave off further spending cuts.
Source : https://www.theatlantic.com/politics/archive/2017/09/gop-decay-of-political-norms/540165/