How did Gallup manage to blow the election?

Obama prevailed in the national popular vote by a nearly 4 percentage point margin. Gallup’s final pre-election poll, however, showed Romney leading Obama 49 to 48 percent. …

Since the election, the Gallup Poll’s editor-in-chief, Frank Newport, has at times downplayed the significance of his firm’s shortcomings. At a panel in November, he characterized Gallup’s final pre-election poll as “in the range of where it ended up” and “within a point or two” of the final forecasts of other polls. But in late January, he announced that the company was conducting a “comprehensive review” of its polling methods. …

Despite the election results being hailed as a victory for pollsters generally, Gallup’s shortcomings have also led some to question whether the methods of all national polling firms are outdated. …

What went wrong in 2012? One possibility is that Gallup set its cutoff point too low, including too few people. While Gallup’s final poll gave Romney a 1 point edge among likely voters, the results from the same poll for all registered voters gave Obama a 3 point lead (49 to 46 percent), very close to the president’s actual margin of victory of 3.9 points.