The way American presidential elections are now determined, a close election will be decided by one important group: independent voters in a few swing states including Ohio, Pennsylvania, Wisconsin and Florida--and possibly Colorado and/or Iowa.

If the election isn't close, if one candidate wins a landslide, the reason will be independent voters nationally.

The electorate is split into three major groups (Democrats, Republicans and independents), and whoever wins two of these wins the election.

To understand the election, keep an eye on independent voters.