You're both right. "Unaffiliated" votes are the single largest voting block in the U.S. However, the vast majority of unaffiliated votes reliably vote for the s

You're both right. "Unaffiliated" votes are the single largest voting block in the U.S. However, the vast majority of unaffiliated votes reliably vote for the same party in each election, so while they are officially independent of a party, in practice they associate themselves with a party in the way they vote. This discovery and the ability to quantify it was one of the breakthroughs of the Obama campaign in 2008 (the Bush campaign did this too, but the Obama folks really brought it to the next level).