Nationwide opinion polling for the 2008 United States presidential election

This article provides a list of scientific, nationwide public opinion polls that were conducted relating to the 2008 United States presidential election.
Presidential election.
Two-way contest: Barack Obama vs John McCain.
Democratic nominee vs. Republican nominee.
Margin shading indicates candidate in lead. Red = John McCain; Blue = Barack Obama
Three-way contest
Earlier polls.
Two-way contest.
"Related article: Graphical Representations of Two-Way Contest Data"
Democratic nominee vs. Republican nominee.
Three-way race
Four-way race
Three-way contest.
See 
Other polls.
Candidate distinctions.
Would you be willing to vote for a thrice-married candidate in 2008?
Would you be willing to vote for a seventy-two year old candidate in 2008?