Article II of the Constitution states that if no presidential candidate receives a majority of votes, the House is to select the winner "from the five highest on the list." No one in 1787 envisioned presidential elections with only two candidates. The Framers figured that lots of people would run.

The same goes for the House of Representatives. With the initial election machinery left largely to the states, the field of candidates proved wide in all 13 states. In the first House election, five candidates for Delaware's lone seat garnered votes. New Hampshire counted votes for 10 candidates vying for three seats. Massachusetts' eight seats had more than 40 candidates.

America, unfortunately, has devolved into a two-party (and two-candidate) system. The benefits behind this approach -- efficiency and fidelity -- do not outweigh its costs. In particular, America's political duopoly suppresses free thought. The two major parties silence dissident voices with promises and penalties; sacred party beliefs and "taboo" topics are squelched in the name of loyalty. An austere marketplace of slogans and codes has consequently emerged, with two parties marginally competing over voters in the middle. I say marginally because the modern Republican and Democratic platforms are not that different.

The 2004 election offers several illustrations, ranging from the military invasion of Iraq to political invocations of the deity. Two examples that caught my eye are same-sex marriage and the federal government's criminalization of marijuana.

Same-sex marriage bolted to the headlines (and the president's 2004 State of the Union address) after a decision by the Massachusetts Supreme Judicial Court authorizing the practice. Republicans quickly inserted a plank in their national platform condemning same-sex marriage and pushed for a federal constitutional amendment. Democrats contented themselves by arguing that marriage should remain a local concern. To the extent Democrats broached the merits, they argued against gay marriage and for "civil unions." Thus, the two parties agreed on the answer (no) to a controversial constitutional question: that is, whether gay and lesbian couples' marital choices are protected by the Fourteenth Amendment's Equal Protection Clause.

The federal government's regulation of marijuana was thrust to the constitutional forefront in 2004 when the U.S. Supreme Court agreed to decide whether the government had the constitutional authority to regulate home-grown marijuana. Neither of the major-party candidates, President Bush and Sen. John Kerry, argued against the constitutionality of the Controlled Substances Act. Few major-party candidates for federal office discussed the matter. In the end, the major parties again agreed on the answer (yes) to another controversial constitutional question: whether the federal government has the power to criminalize all marijuana possession under the Commerce Clause.

It could be that everyone in America agrees that marijuana is so innately evil that the government can and should prohibit its possession and use. Similarly, Americans might uniformly agree that same-sex marriage is so bad that it deserves no federal protection. National polls in the run-up to the 2004 elections, however, suggested that neither consensus existed: more than one-third of Americans favored the outright legalization of marijuana, and an even larger percentage favored legalizing same-sex marriage.

The sterile nature of the constitutional debate on these topics illustrates a flaw in America's de facto two-party system. Rather than risk honest curiosity and intellectual inquiry, the two major parties flock to conventional conclusions. Political dialogue is stagnant, choice is meaningless and campaign contributions drive electoral outcomes.

How can this be changed? One way is for voters to support third parties and minor candidates. Even if they cannot win, these players change outcomes, as Ralph Nader proved to Democrats in 2000. (Republicans James Blaine and Charles Evans Hughes discovered this in 1884 and 1916, respectively. Both would likely have won but for the presence of Prohibition Party candidates.)

Such candidates sometimes win or come so close that the political landscape is forever changed. Examples are "progressive" candidates such as Theodore Roosevelt and Eugene V. Debs in the early part of the 20th century.

Of course, this is the major parties' biggest complaint. Minor candidates, they claim, are egotistical "spoilers." But that is what the status quo always says about those who threaten change. The truth is that minor candidates play an important role. Their presence facilitates political evolution and keeps the powers-that-be honest. Minor candidates are an important check on political tyranny. The Framers knew this to be a self-evident truth.

What can voters do to support this political check? In the long run, they can see that restrictive ballot-access laws are repealed or amended. Ask your favored candidates what they think about laws that make it virtually impossible for minor candidates to run. If they favor them or fail to provide an intelligent answer, vote for someone else -- if you can.

In the short run, voters can sign petitions that are circulated by minor candidates. Grass-roots efforts can prevail. Put minor candidates on the ballot even if you do not intend to vote for them. That way, at least, you will have someone to vote for if your favored candidate can't answer your questions.

Mark R. Brown teaches constitutional law at Capital University.

mbrown@law.capital.edu