Instead of looking at one national election, political scientists tend to analyze results as 50 state elections, to see deeper trends. Look at the states Obama won in 2008, representing 365 electoral votes. It was always a stretch that Obama would permanently turn North Carolina and Indiana blue, since he took those states by a few thousand votes in 2008. Only a decidedly weak Republican president and presidential candidate made those victories possible. Not surprisingly, NC and Indiana shifted back to the Republican fold in 2010, the continuation of a historic trend going back decades.
A major concern for Obama is the states where he and his party have had the upper hand, but don't any more. The formerly true blue state of Wisconsin comes to mind, where independents abandoned Senator Russ Feingold in favor of a not-very-impressive businessman with almost no public record, in part because of Feingold's stand on health care reform. And almost overnight, the formerly blue state of Maine turned red. The purple or swing states of Ohio, Pennsylvania, Arizona, Virginia, Missouri and Florida also bear watching. Washington Post:
"History shows ample precedent for a comeback two years from now, Democratic leaders say, but it will take two things: The economy will have to improve in ways that Americans can feel in their daily lives, and independent voters will have to regain confidence in Obama, who now has a second chance to prove he is the post-partisan conciliatory figure they voted for in 2008."