A rising tide lifts all assumptions.
VIRGINIA provides an example of big partisan changes driven by population growth. Obama's 2008 showing (52.6%) was the best for a Democrat since Johnson in 1964 (53.5%), but the electorate over that period more than tripled, from 1,042,267 to 3,723,260. So Obama set a record for a Democratic raw-vote margin (234,527), even though Democrats routinely carried the state by at least 20 points during the "Solid South" era of the first half of the 20th century. Of course, the state's growth is what turned Virginia safely red for nine straight elections before 2008, so neither party is feeling secure about the state in 2012.