Before television, the presidential election cycle was relatively brief. Campaigning would take place between the conventions (in the summer) and the election (that November). Primaries were held, but candidates wouldn't run full-fledged campaigns to win support. Instead, each state's party would send delegates to the national convention without consulting the public. At the convention, the delegates voted on the candidate they wanted to represent the party [source: Dover].
That all began to change in 1952, when the national party conventions were first televised. The thought was that covering the conventions would give the public a window into the way the parties made decisions. Few probably expected that the reverse would happen -- that the coverage would move the parties to change the way they ran conventions [source: Kaid]. Playing up to the cameras, conventions became a venue for party leaders and rising stars to make speeches, not places where actual decisions were made. Today, the convention is mostly an opportunity for the candidates to stage strong starts to the general election campaign. The voting that takes place at the conventions is mostly ceremonial [source: Dover].
As the conventions have become less important, the primaries have become more important. The news coverage of the campaign begins one, even two years before the first primary election is held, and two to three years before the general election. This has become especially pronounced as the 24-hour news networks have risen in popularity and have huge amounts of air time to fill. For example, as early as the summer of 2009, pollsters were already testing the waters for which candidates might win the election in 2012 [source: Rasmussen Reports].