Two of the front runners among Republicans couldn't be more different.  Huckabee, the former baptist preacher is  socially conservative, fiscally moderate and has a strong and growing base.  Rudy Giuliani, is socially liberal, fiscallly a bit on the conservative side, and has generated his broad base of support because he is seen as the candidate who can beat Hillary. Fred Thompson would  at first glance appear to be the best candidate for Republicans.  He has wide name recognition, a track record of supporting the constitution, and he looks presidential. He also doesn't campaign very well, and that's at least moderately important in a presidential campaign. Ron Paul is either an absolute nut-case, or a genius, depending on who you ask. He is good at raising money, and has absolutely no chance of winning. John McCain has become the Dick Gephart of the Republican party. He seems like a solid candidate, who can't ever seem to rise to the top in the primaries.
The Democrats don't have it much better.  Hillary Clinton's star is fading fast.  She performs terribly in debates, and she can't answer simple position questions without wetting her finger and holding it up. But her biggest problem may be she hasn't clearly created a case of what she would do as president. Even her most ardent supporters have no idea what her direction would be for the country.  Barack Obama has Oprah's support, which is worth a lot.  He is a great speech maker, and he does step out of the mold and take a chance now and again ("I would talk to the Iranians.").
If Obama had a bit more experience, he would have a more measurable track record, and would probably be running away with the nomination. But his unknowns are hurting him. 
Some of his exasperated supporters are wrongly assuming a black man can't get elected in the United States yet. This is complete bullshit.  Colin Powell would have won.  He enjoyed wide spread support, Obama, at this point, doesn't.
John Edwards has exhibited a thorough knowledge of the issues. He has some decent ideas, if you're a Democrat, a track record that can be checked, and he's got more experience than Barack Obama.  He also comes across as a bit of a flake.  And sometimes, it's laughable. 
The Democrats also have Joe Biden, Christopher Dodd, and Bill Richardson. All decent men, with leadership experience, solid Democratic ideals, years of experience, an internal network that would allow them to build effective cabinets, and they are likable.  None of them has a chance. 
Why?  The Democratic party has come full circle.  FDR was able to unify the party around a few core issues.  The biggest of which was building a basic safety net for the average working American.  The Democratic party today is so factionalized, that the nominee with a long track record, and broad appeal, can't possibly win. You have to pick three or four factions, go hard after them, and hope everyone else goes along for the ride.
The Republicans on the other hand have a bit too much "diversity" in their candidates.  This is both good and bad.  If you can't find a Republican  you support, you're just not looking hard enough. On the other hand, they are so drastically different, it's going to be difficult to build a broad support base once the nomination has been secured.
What a mess!
So what's the lesson?  The party leaders are going to have to make a choice.  They should pick no more than two or three candidates, and then thrown as much support behind them as possible.  This will allow the nominee to shore up a base, and give a few front runners much more exposure. 

The big winners in 2008 may be those states that didn't push their primaries up so early in the process.  One thing is for sure, Iowa and New Hampshire have never been so un-important in an election.  South Carolina?  perhaps a bit more, but Florida, Ohio, California, and some of the other big states in the middle may hold the cards this time out.  And who knows, one party may actually go down to the wire in '08.