You will not be able to choose the next president of the United States. Your single vote will not make any difference. There will likely be about 100 million votes cast in this election. While it's possible that the result will be a 50 million to 50 million tie until you show up at the voting booth, I will (if you call me here at the magazine) bet everything I own that it won't happen. Not unless Frank Capra becomes God and orchestrates the election in the same fashion as his populist movies.
Simply because your vote is impotent, however, does not mean necessarily that you should stay home on election day. A single person's cheering at a football game won't affect the result, but people nonetheless take pleasure from expressing their support. Voting is your way of cheering for your party, and for the institution of republican democracy.
Voting is also a test of moral integrity that some people fail miserably. One reason it is difficult for third-party candidates to succeed is the tendency for people to think a vote for such candidates is "wasted." Even though they prefer some third-party ideology, some people aren't willing to "throw their vote away." They know Ron Paul can't win, for example, so they vote for Bush because he's better than Dukakis (or vice versa). This is illogical, since it's based on the false premise that they can make a difference in the election; but even worse, it's sleazy. People who vote this way sacrifice their principles and honor for the billion-to-one chance of being rewarded (that is, influencing the election). Not even the most corrupt Pentagon bribe-taker would compromise his integrity on such cheap odds.
If you like a third-party candidate in this election, vote your principles. And if you don't like anybody who's running, pick a third-party candidate at random—as a vote to break the two-party monopoly on political power. Most states have petition requirements and other ballot restrictions that help preserve that monopoly, but in large part the voting public is to blame for making Michael Dukakis and George Bush the two likeliest alternatives for president.
There's a joke about two guys walking across the tundra when suddenly they are charged by a polar bear. One guy starts to put on his snowshoes, and the other says, "What are you doing? You'll never outrun that bear." The first guy replies, "I don't have to. I just have to outrun you." Dukakis can alienate gay voters on the foster-parenting issue, for example, because he knows that they will vote for him nonetheless. He need only be better than Bush. Bush can scare conservatives with his new-found environmentalism, as long as his plans are less onerous than Dukakis's. Only when more candidates are competing for votes will voters have real choice. Remember the days of telephone monopoly? If you wanted a phone, you were offered only one color and one style. We have the same problem with presidents.