Think about this analogy. The peanut butter industry is really huge, and there are many brand names that make it up. Each brand has a bit of a different taste to it, and each different taste has a different label on the front: Jiff, Skippy, and Peter Pan. Political parties have, in recent years, worked the same way. There is a big pool of politicians and many ideals that distinguish them from one another. They then identify themselves with a label: Democrat, Republican, and Independent.
The modern political party is just big umbrella. Take the Republicans for instance. There are the staunch Conservatives, the Libertarian-leaning conservatives, the moderate conservatives, and liberals who don't support Obama. I can tell you for one fact that around 40% of Americans ever election identify themselves as Independents and do not commit to a party. 31% identify themselves as Democrats and 27% identify themselves as Republicans. So, as you can see, almost half of our country's population is already voting for a candidate and not a party.
It is obvious that the public is starting to run away from the political party idea. The general public is voting for the ideologies of the candidate and what they stand for, and not what label has been applied to them. Some Republicans will say that Mitt Romney is too moderate, but on that voting ticket, you will be voting for Mitt Romney (R). The (R) obviously stands for Republican. The staunch conservative and liberal political parties have very little influence on a more moderate voting public, nowadays. The traditional set of politics established by the 1800 election has finally fallen to a more recent way of viewing candidates, the better way: based on the issues.