The US presidential election campaign has entered the final sprint toward Election Day in November.

The two major party candidates, Democrat Hillary Clinton and Republican Donald Trump, are the most disliked candidates in recent memory. Two minor party candidates, the Libertarian Party’s Gary Johnson and the Green Party’s Jill Stein, are together projected to drain about 10 percent of votes from major party candidates, the highest percentage since 1992. Polls show that the major party candidates are particularly unpopular with voters under the age of 34, with 40 percent leaning toward minor parties.

The US has a long history of third-party candidates for president, but Abraham Lincoln is the only third party candidate ever to win, which turned his young Republican Party into a major party overnight. In 1912, former President Theodore Roosevelt ran as a third party candidate and received more votes than the Republican incumbent President William Taft. The Republican split caused Democrat Woodrow Wilson to win.

Until the Great Depression, a number of elections were four-way contests. Franklin Roosevelt’s popularity from 1932 to 1944 and the long Cold War that followed made it difficult for left-wing parties to flourish and the strongest third-party candidates came from the right. The only four-way race was 1948, when two minor party candidates received a total of 5 percent.

The low popularity of the two major party candidates combined with the younger generation’s hunger for change have turned this year’s contest into a rare four-way race. This will most certainly result in the winner receiving less than 50 percent of the popular vote, which would make him or her a “minority president.”

The unusual race this year raises interesting questions. Will the strength of minor parties continue? If so, how will it affect the major parties? Why have the two parties remained so strong over time?

Of the two minor parties, the Libertarian Party, is the strongest and Gary Johnson is doing well in the polls. Founded in 1971, the party has fielded a candidate in every election since 1972. Its best showing was in 1980, when it received a little over 1 percent of votes. If Gary Johnson receives 7 to 8 percent, as the polls indicate he might, that would be a stunning increase. Nationally, the Libertarians have few elected officials, but their candidates have been receiving ever higher percentages of votes.

The Green Party is smaller and younger. Founded in 2000, the party’s best showing was in 2000, when consumer rights activist Ralph Nader received 2.7 percent of votes. Many believe that he drained votes from Al Gore, which cost him the election in the tight race against George W. Bush.

The Green Party has struggled to overcome its image as an immature spoiler party. Jill Stein received a tiny 0.4 percent of votes in 2012, but could get 2 to 3 percent this year, which could be better than Nader’s showing in 2000.

The Libertarian Party has gained momentum because of Republican discontent with Donald Trump. The party’s ideology of “small government, maximum freedom” may not appeal to younger voters who want more government intervention in society. The only real way for the Libertarian Party to move forward is to continue to attract disgruntled Republicans. A Trump victory would ensure a plentiful supply of such Republicans, but a Republican defeat would open the door for a unifying figure to emerge in 2020.

The ghost of the 2000 election continues to trouble the Green Party. A good showing, combined with a Trump victory would reopen the wounds of 2000, thus damaging the party’s image among left-wing voters.

A good showing, combined with a Clinton victory, however, would help exorcise the ghost of 2000, giving the party an important psychological boost. The biggest challenge for the Greens is to move beyond the fringe to being a possible governing party. To do so, they should choose presidential nominees with political experience.

In the end, the structural impediments for third parties in the US are too difficult to overcome. The US has a first-past-the-post system in which the candidate with the most votes wins and the other candidates get nothing.

This system encourages groups to develop political alliances to increase chances of election victory. In the process, smaller groups disband and their members drift to one of the larger groups. This makes it very difficult for smaller groups to grow. It also explains why the surest way for a minor party to become major is the breakup of an existing large group. It also explains why minor parties in first-past-the-post Korea fade so quickly after they lose. Food for thought as the Korean presidential election approaches.

By Robert J. Fouser

Robert J. Fouser is a former associate professor of Korean language education at Seoul National University. He writes on Korea from Ann Arbor, Michigan. -- Ed.