Electoral College election map 2012: Democratic 'blue wall' crucial for President Obama victory

WASHINGTON (CNN) -- With Florida finally called and the 2012 presidential election falling into the rear view mirror, here's a look at another reason why President Barack Obama won re-election: The Democrats held their "blue wall" -- the cluster of eastern, Midwest and western states that have traditionally gone Democratic and were crucial to his victory.

"Democrats held the entire 'blue wall'. They have now won 18 states in at least six consecutive elections, the most states they have won that often ever, since the formation of the modern party system in 1828," says CNN Senior Political Analyst and National Journal Editorial Director Ron Brownstein.

What states make up this so-called "blue wall"?

Start in the Mid-Atlantic and head north into New England: Maryland, Delaware, Pennsylvania, New Jersey, New York, Connecticut, Rhode Island, Massachusetts, Vermont and Maine. The only state not included in this list is New Hampshire, a perennial swing state.

Add three West Coast states (California, Oregon, and Washington State) and Hawaii, and the reliably blue Midwestern states (Illinois, Michigan, Minnesota, and Wisconsin).

Put all those states together and add the District of Columbia, and you total 242 electoral votes. That's a nice starting point for any Democratic nominee, considering that 270 is the magic number needed to win the White House.

Many of the October public opinion polls indicated the president with the slight edge in the eight swing states (according to CNN's electoral map). That may explain why Romney became the latest GOP presidential nominee to try to make a last-minute bid to breach the "blue wall," with moves in Pennsylvania, Minnesota and Michigan. But once again, it didn't work.

As the nation's demographics continue to shift, New Mexico and even Nevada may eventually be added to the "blue wall," making the GOP's path to the presidency increasingly difficult.

"Until Republicans can crack the 'blue wall,' Democrats start with a base of 242 Electoral College votes, which means a GOP nominee must thread the needle, or practically run the table, to get to 270," adds Brownstein.

The Republicans, on the other hand, have their "red wall" -- the large southern, Plains and Mountain states that cover a lot of geography but not as many electoral votes, like Utah, Idaho, Texas, Mississippi, South Carolina and others. But together, the "red wall" only nets Republicans 177 electoral votes at most.

The big question confronting Republicans: "how to crack that wall"?

With director Steven Spielberg's new film "Lincoln" opening to critical praise, CNN Polling Director Keating Holland sees a comparison of today's "blue wall" to the coalition of states that put Republican Abraham Lincoln in the White House in 1860.

"There are some differences: Washington and Hawaii weren't in the Union at the time and Delaware and Maryland were slave-holding states. Lincoln also added New Hampshire, Iowa and Indiana to the list of "blue wall" states in order to win the White House," says Holland.

"The GOP was the 'big government' party back then, willing to use the government's power not just to resolve the slavery issue, but also for big government programs like the Transcontinental Railroad, the land-grant college program, and the Homestead Act -- all projects which a lot of Democrats opposed at the time as going beyond the bounds of the government's authority. The parties have changed sides, but it looks like the underlying attitudes in those states that put them in the 'blue wall' category may be similar to what they were in Lincoln's time," adds Holland.