We talk as though the United States has only two political parties, but of course there are always dozens of other parties that put up candidates for whom we may vote. Most receive a tiny percentage of the vote, but they provide a vehicle for voters who are unhappy enough with the two dominant parties to look for a way of registering a protest. Nationwide, the two minor parties that currently show the most durability are the Greens (on the left) and the Libertarians (on the right).

Yet our history has been consistently marked by the dominance of two parties that share almost all elected offices and alternate in the presidency. Only once since the formation of modern political parties in the 1820s has a third party succeeded in permanently displacing one of the major parties. That was in the 1850s when the Republicans replaced the Whigs over a series of elections culminating in 1860, on the eve of the Civil War. The country was even more deeply divided then than it is now, particularly over slavery, and both parties split. The Whigs did not survive it; the Democrats did, but in running three presidential candidates in 1860, they let the Republican nominee, Abraham Lincoln, win with a minority of the vote.

There have been several other third party candidacies that were more than mere protests; a few have affected the outcome, usually by throwing the victory to the party less desired by the third party voters. The classic was in 1912, when Teddy Roosevelt’s Bull Moose Progressives split from the Republicans, came in second, but handed the election to the Democrat, Woodrow Wilson (again winning with a minority of the vote). In 1968, when the South was still nominally Democratic, George Wallace channeled the discontent of white Southerners to take several Deep South states and hand a minority victory to Richard Nixon. In 1980, liberal Republican John Anderson ran an independent campaign that took votes from Jimmy Carter and gave the victory to Ronald Reagan. In 1992, Ross Perot’s independent run sank George H. W. Bush’s reelection campaign, letting an obscure Arkansas governor named Bill Clinton win. In 2000, Ralph Nader’s Green Party candidacy took enough votes from Al Gore to hand the election to the Supreme Court, which appointed George W. Bush.

When few people are really happy with the two major parties, why is it so difficult for third parties to get beyond the spoiler role?

When few people are really happy with the two major parties, why is it so difficult for third parties to get beyond the spoiler role? The way our government and our elections are structured has a lot to to do with it. For a start, we have one overwhelmingly important elective office, the presidency. Only one person can win that election, so voters naturally want to vote for a candidate who has a reasonable chance of winning. Only two candidates are likely to have such a chance. Candidates not seen to have a chance tend not to get many votes.

Second, the same winner-take-all dynamic applies in virtually every other elective office in the country, right down to local councils. So in any given race, there will only be two serious candidates. Indeed, in almost all states, our peculiar institution, the Electoral College, operates on a winner-take-all basis. We could, in principle, have a separate two-party system in each of these local elections, except that…

Third, parties that are well-organized on a state or national level have a chance to link all the local races so that one party captures a legislative majority. This is what the Republicans did to replace the Whigs. It is well-established worldwide that countries with our type of winner-take-all election rules have a strong tendency toward two dominant parties.

How could this iron cage be breached? Two major changes would probably do it, but would require amending the Constitution. The first would be to convert to a parliamentary system, in which the Chief Executive would be a Prime Minister holding office as long as s/he has a parliamentary majority. The second change would be proportional representation (PR): whatever percent of the vote a party received would be reflected in the percentage of parliamentary seats. It is well-established worldwide that PR tends to promote multiparty, rather than two-party systems.

Constitutional amendments are hard. If we can’t even agree to abolish the Electoral College, how can we expect to agree on such major surgery as these two reforms would entail? Especially when it would be up to officeholders of the two major parties who would have to agree. So the deck is completely stacked against third parties.

In the current campaign, both major parties risk a split and a possible third party run. If Donald Trump is denied the Republican nomination, he might well run as an independent or third party candidate. If Bernie Sanders falls short, some of his supporters are so opposed to Hillary Clinton that they could favor a third party run (though there is no sign that Sanders, in the end, would bolt the party).

Here the model might be 1948, when Strom Thurmond bolted the Democrats and ran as a Dixiecrat, while former Vice President Henry Wallace ran as a Progressive. President Harry Truman was the Democratic candidate; Thomas Dewey the Republican. In effect, the Democrats lost both their left wing, to Wallace, and their right wing, to Thurmond, but Truman unexpectedly won anyway.

The Electoral College was consequential in 1948, and might be again in 2016. Thurmond and Wallace got nearly the same number of votes, but Thurmond, his votes concentrated in the Deep South, won four states and 39 electoral votes. Wallace’s support was much broader across the nation, but nowhere was he able to win a state: even though Wallace’s popular vote was almost the same as Thurmond’s, he won no electoral votes.

So let’s suppose that both Trump and Sanders run as independents. Trump’s support in the South might well get him to victory in several states. He might even outdo the official Republican nominee (likely Ted Cruz), as Teddy Roosevelt did in 1912. Sanders, on the other hand, running against Hillary Clinton as the Democratic candidate, would be hard-pressed to win any state, but he could draw enough votes to allow Trump to defeat Clinton in some states. It is hard to predict whether that would be enough to let Trump win nationally.

Most likely, a Trump candidacy would split the GOP vote and hand the election to Clinton, UNLESS a Sanders candidacy tipped enough states to Trump to let him win with a minority of the vote. Each of these possible outcomes would be perverse, the first for Trump voters, the second for Sanders voters. That’s the political world we are trapped in. Deal with it.

John Peeler