What does this remind me of?

Apparently the Mexican election was decided by a very narrow margin.

With all of the 41 million votes counted, Calderon of President Vicente Fox's National Action Party had 35.88 percent to 35.31 percent for Lopez Obrador, of the Democratic Revolution Party. The two were separated by about 220,000 votes.

According to the story 300,000 votes were cast in favor of Pat Buchanon. That's a joke guys.

The amazing thing about this though is that almost 30% of the votes went to other candidates. Why can't third party candidates in the U.S. gain that kind of support?