One of the cornerstones of a vibrant democracy is citizens’ ability to influence government through voting. In order for that influence to be meaningful, citizens must send clear signals to their leaders about what they wish the government to do. It only makes sense, then, that a democracy will benefit if voters have several clearly differentiated options available to them at the polls on Election Day. Having these options means voters can select a candidate who more closely represents their own preferences on the important issues of the day. It also gives individuals who are considering voting a reason to participate. After all, you are more likely to vote if you care about who wins and who loses. The existence of two major parties, especially in our present era of strong parties, leads to sharp distinctions between the candidates and between the party organizations.
Why do we have two parties? The two-party system came into being because the structure of U.S. elections, with one seat tied to a geographic district, tends to lead to dominance by two major political parties. Even when there are other options on the ballot, most voters understand that minor parties have no real chance of winning even a single office. Hence, they vote for candidates of the two major parties in order to support a potential winner. Of the 535 members of the House and Senate, only a handful identify as something other than Republican or Democrat. Third parties have fared no better in presidential elections. No third-party candidate has ever won the presidency. Some historians or political scientists might consider Abraham Lincoln to have been such a candidate, but in 1860, the Republicans were a major party that had subsumed members of earlier parties, such as the Whig Party, and they were the only major party other than the Democratic Party.