Congress requires states to draw single-member districts.
But presidential approval also became a surrogate measure of national unity and patriotism.
Presidents are elected not by direct popular vote but by 538 members of the Electoral College.
America is an outlier in the world of democracies when it comes to the structure and conduct of elections.
A healthy degree of party unity among Democrats and Republicans has deteriorated into bitter partisan warfare.
Votes in federal elections are cast and counted in a highly decentralized and variable fashion, with no uniform ballots and few national standards.
With the parties at virtual parity and the ideological gulf between them never greater, the stakes of majority control of Congress are extremely high.
Responsibility for overseeing the implementation of election law typically resides with partisan officials, many with public stakes in the election outcome.
While Republican voters have remained universally supportive of their President, Democrats and Independents are returning to a more naturally critical stance.
In addition to the decline in competition, American politics today is characterized by a growing ideological polarization between the two major political parties.