The presidential election's outcome could be considered a victory for pollsters like Nate Silver who saw President Obama as the favorite even before Election Day arrived. But that was not the case for the esteemed Gallup Organization. Gallup's poll had shown Mitt Romney with a large lead among likely voters 10 days before the Election. However, Obama managed to win by about 3 percentage points.

So how did Gallup get it wrong? Possible reasons for the inaccuracy:

• Gallup's likely-voter model uses seven questions to award points and determine who will actually cast ballots.
• The pollsters underrepresented younger respondents in its likely voters measures.
• Issues with Gallup's intial sampling may be to blame.
• Gallup makes adjustments to ensure the initial sample of adults is reflective of the overall population-- adjustments that could be flawed.

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