Final answer:
The U.S. electoral system, especially the winner-take-all voting format and the Electoral College, along with strategic voting and historical precedents, promotes a two-party political system predominated by the Republican and Democratic parties.
Step-by-step explanation:
Several features of the electoral system tend to promote the existence of two major parties. In the United States, a winner-take-all or plurality voting system is one such feature that has contributed to the prevalence of a binary political landscape, predominantly occupied by the Republicans and the Democrats. This system creates difficulties for third parties to gain traction, as voters do not wish to cast their votes wastefully on candidates with slim chances of winning, hence they are inclined to support one of the two major parties.
Another factor influencing the two-party dominance is the country's historical context. The initial divide between the Federalists and the Jeffersonian Republicans set a precedent for a dual-party system, which has persisted through various realignments and changes. The need for political parties to form broad coalitions and appeal to the moderate majority has maintained the emphasis on the two dominant parties.