Quote from Maverick74:
Historically undecideds break for the challenger.
If that was the case incumbent Presidents wouldn't have a 70 % win rate
Incumbents also usually gain 7 points from summer polls
http://fivethirtyeight.blogs.nytimes.com/2012/07/22/do-presidential-polls-break-toward-challengers/
"The other anomaly has been in the summer months â June, July and August. In these months, the polls have tended to low ball the position of the incumbent partyâs candidate. In July polls, for instance, the incumbent-party candidate has trailed by an average of 4 points in elections since 1968. However, the incumbent-party candidate has actually won these elections by an average of a little more than 3 points. In other words, there has been a seven-point swing on average toward the incumbent partyâs candidate from the July polls until November."

:eek:
