If you compare the 2004 Presidential Election to 2000; and 2012 to 2008, there is not much electoral change.
George Bush carried 30 states.
Al Gore carried 20 states and DC.
George Bush carried 31 states
John Kerry carried 19 states and DC
John Kerry took New Hampshire the second time but lost Iowa and New Mexico-net loss of one state for the Democrats.
Barack Obama carried 28 states and DC
John McCain carried 22 states
Barack Obama carried 26 states and DC
Mitt Romney carried 24 states.
North Carolina and Indiana went Republican in 2012 after voting for Obama in 2008
Since 1900, the only other times that an incumbent President won re-election by declining majorities were anomalies that will not happen again. Not the results for Franklin Roosevelt below.
1932-won 42 states and 57% of the popular vote.
1936-won 46 states and 60% of the popular vote.
1940-won 38 states and 55% of the popular vote
1944-won 36 states and 52% of the popular vote.