That has become a mostly irrelevant exercise in recent presidential elections. But in the event of a razor-thin finish, or a 269-vote tie, every elector will suddenly wield great power.
"If there appears to be a tie, then faithless electors become a big problem, and we could have a real mess on our hands," said Robert W. Bennett, a constitutional law professor at Northwestern University who has written extensively about the Electoral College.
In the course of writing a book on presidential electors, Alexander interviewed more than half of the electors who participated in the 2000, 2004 and 2008 elections. Of the 2004 group, 10% said they considered voting for someone other than to whom they were pledged. In 2008, 11% said the same.
Many told Alexander they were lobbied or pressured by someone to change their allegiance -- sometimes in person, sometimes by anonymous e-mails and phone calls -- in the period between Election Day and mid-December, when the Electoral College votes.
"If it's really close, you would expect to see massive lobbying campaigns," Alexander said. "Most do follow the herd, but not all, and that becomes the question in a close election. What happens at the margins?"
Despite being party loyalists, he said, electors are regular people with their own biases and political inclinations. In rare cases, they make them known.
Throughout this past spring and summer, Ron Paul's devoted supporters worked furiously to elect their own as electors at state party conventions.
"They are trying to be the revolution to the Electoral College," Alexander said.