Now, neither the Democrats nor the Republicans are Nazis, but the principle remains the same. Whatever your personal ideological leanings, it's just as likely that one party will be right about X and the other will be wrong. Blurring right and wrong isn't necessarily an improvement. Blending black and white may make you feel good about your capacity for nuanced thinking, but in terms of public policy, gray is often worse than either. For example, California's recent electricity crisis was the result of trying to deregulate "a little," which is worse than not at all.
This irony is completely lost in the public debate; the more strongly held your beliefs, the less seriously the media take you. What's ironic about this is that people of strong political or ideological views tend to know what they are talking about more than people who have no strong views at all. This is a fact confirmed by common sense. You need to know about something before you can have strong feelings on it.
If you wait until the last minute to figure out whom to vote for; if you can't tell the differences between the parties and their candidates (and you're not politically exotic - i.e., an anarchist or a libertarian); if you think voting is like a Chinese menu where you can pick a little from here and a little from there; then the odds are you don't know very much about the political system. You may be a brilliant neurosurgeon, but I know interns who are sharper than you about politics.
The reasons for this odd state of affairs are complex. We tend to fetishize independents because we live in an age when nonconformity is the new conformity. When people are designing their own religions and their own moral codes, is it any shock that they're designing their own politics, too? Also, the parties themselves are weaker today than they've been at pretty much any time in American history, so it's just easier for most folks to buck them. And the press itself is deeply cynical about politics, believing that true believers are all freaks or gauche - and therefore that the Americans who echo their own views are the most wise.
But the biggest reason is structural. By election day, the bases of the parties have already made up their minds, which leaves only the procrastinators and prima donnas to scrounge for. This turns "swing-voters" into kingmakers even when they don't deserve to be. So politicians flatter them. The news networks treat them like oracular geniuses. But their only genius is to have been too lazy to pay attention until the last minute.
For example, in 2000 Michelle Cottle of The New Republic covered one focus group set up to watch the presidential debates. One woman, Yeshai Gibli, explained that she went into debate liking Gore but after watching Bush and Gore debate she decided that Gore wasn't left-wing enough - so she was voting for Bush. Is that any way to choose a president?