-Nearly 55% of Americans receive some sort of government check and/or subsidy. Republicans are unlikely to win many of those voters with their talks of spending cuts to social programs(but not the Defense budget).
-More Americans than ever are associating with Atheism or barely acknowledging religion. These voters are unlikely to side with anti-abortion crusaders and the Rick Santorum-types.
-The expanding and more influential Hispanic populations are highly unlikely to vote for a party whose base members clamor for strict immigration controls. The Hispanic unity on this issue is puzzling as granting amnesty or lax immigration would actually be severely detrimental to much of its population, it actually comes as no surprise as they show a great deal of togetherness since they have this one similar attribute: they speak Spanish.
-Democratic voters represent literally a quilt-work hodgepodge of voters: gays, racial minorities, religious blacks, the rich, city dwellers, Jews, and the highly educated. In spite of the obvious conflicts of interest presented amongst all these groups, few, if any, would ever be persuaded to go over to the Republican side.