democracy?

"caucuses" and "primaries" can probably best be seen as "elections to get into the election". As many of you overseas are aware, we have a two-party system in this country. At present, both sides are fielding 6 candidates apiece, all of which have very staunch supporters. There's also (at this stage of the game), generally 4-5 independent candidates, one or two socialists, a KKK nutjob, and someone who thinks the south should cede from the union...or wants to reinstate the gold standard...anyway...if we held the election now, no one would snatch more than 20% of the vote, and then the president would exactly have the "mandate from the masses" necessary to give his office any credibility (weather it actually HAS any is up to you...I'm not sure at this point)

when you vote in a primary, you help determine which of the numerous candidates is represented by a particular party. It forces the parties to run like little democracies, you get to pick the presidential contender in each one.
They also select which names are actually going to go on the ballot. Technically, you can vote for anyone, but to actually have your name printed on a voting ballot, you need to score a certain number of votes (it's actually pretty small), in one of these elections.