From a Wall Street Journal essay by Gerald F. Seib headlined “Could a Third Party Finally Do It?”:

The recent history of independent and third-party presidential runs in this country is easy to summarize: High hopes followed by dashed expectations.

Back in 1968, George Wallace, proclaiming there wasn’t a “dime’s worth of difference” between the two parties, ran as a third-party candidate, won more than 13% of the vote and carried five Southern states. He didn’t really alter the outcome of that race, however, though he did help move white Southerners out of the Democratic Party and into the Republican column and thereby altered the shape of both parties.