This is why President Obama will win this election. [View all]

In 2008, about a fourth of all voters were contacted in some way by the Obama campaign. Mr. McCain’s campaign contacted 18 percent of general-election voters. A FiveThirtyEight study from just after the 2008 election found that “each marginal 10-point advantage in contact rate translated into a marginal 3-point gain in the popular vote in that state.”