What exactly are you calculating?

I expected Texas voter turnout for a Presidential election to be about 8,075,000. Assuming everyone votes either for Obama or Romney, averaging the polls gives a probability for each vote of about 0.415 for Obama and 0.595 for Romney. That story fits a binomial distribution, and my vote would be critical if the votes were split evenly.

binopdf(0.5*8075000,8075000,0.415) evaluated to approximately 10^-51120, and at that point I just upped the exponent one rather than trying to figure out the electoral college details.