For as long as I have been politically aware, there has been steady clamoring for a third party presidential candidate, an independent rogue who could unite a big enough minority to pull off an upset. Ross Perot gave it his best shot, possibly helping Bill Clinton with sub-majority margins. Ralph Nader also tried, only to de-rail Al Gore in the tight 2000 race. And if the rumors are true, Barack Obama is prepared to do the same if he doesn't win the nomination. This must make the RNC happy, because they have to be doubting that John McCain will win over the conservative base needed for victory in November. I'm doubtful Obama would ever go for it, and would more likely wait his turn, get some experience, and improve his political acumen. He should be wise enough to know that he's too far to the left for middle America's taste in a 3-person race and doesn't currently appeal to "moderates" like McCain can.
But it raises an interesting possibility and it underscores that both parties are in desperate straights at the moment. While Republicans have boasted since 1994 they were a party with all the momentum, and that even when they lost elections it was because of the unity or purity in the conservative movement, that boast can no longer be made. The Republican party is without question divided in the same way the dreaded Democrats are, by trying to appeal to niche voting blocs like evangelicals and one-issue voters, with the one issue usually being abortion. Consequently, the libertarian influence vs. the "compassionate conservative" influence are butting ideological heads, with McCain ending up somewhere in the middle, the last man standing with little support among the purists.
That's not to say the Democratic Party also doesn't have serious problems, notably allegiance to voting blocs of their own. So, if the conservatives are unhappy with their prospective nominee, and if Obama bolts to run an independent campaign, who says this won't turn into a four-horse race? Maybe this is the time for ideological purists to fight it out on both sides, to lay it out on the table, to force America to embrace ideas over a party, especially if that party has failed them, which both sides seem to be saying.
This, of course, isn't likely, and America doesn't seem possible of embracing a German-style government, where minority parties maintain substantial clout, even in the face of no majority win. But there might be a temptation to open up the floodgates if Obama breaks rank with the DNC. After all, presumably, the winner would only need a higher percentage than the other three candidates to be president, as Bill Clinton showed in 1992 and 1996, and it wouldn't necessarily dictate that the congressional elections would need to follow suit as they do in Germany, or other European nations. Perhaps a third candidate on the left would open up the path for a fourth candidate on the right, perhaps someone who conservatives view as electable and ideologically pure, maybe a Fred Thompson/Duncan Hunter ticket.
I'd be amazed if we ever left the two-party system in any branch of government. Too much of our government, and even our culture, is built around a basic understanding of majority rule. In that sense, we more accurately represent a republic than a democracy, or a mobocracy. The loudest or largest minority of many minorities does not the law-maker make. Only the one who has the ability to sell himself and/or his ideas to a majority of the public can claim such a mantle. But there is the possibility that in a one-person office like the presidency, in a year where there are no clear front-runners, four candidates would emerge just as soon as three.