I agree with Bob here. Washington columnists just never seem to learn with this stuff. To say the Democratic race is over, with Hillary and Obama being the only contenders, just belies history.
Overall, I like Dan Balz' writing and think this piece is well worth a read. But does Balz remember where Clinton and Carter, the last two Democratic presidents, were at this point in 1992 and 1976? Does he remember how a guy named Reagan almost knocked off a sitting president in 1976 in the primaries, and how Gary Hart looked like he could go all the way (in more ways than one) in 1988? How about the McCain surprise in 2000 (different than the more recent McCain surprise, that he is Bush in Arizona drag) or the fact that the race was Howard Dean's to lose in 2004?
I could give many more examples, but I think you get the picture. Rarely has there been a race where it was a foregone conclusion who the party nominee was, not even with Bush Sr. as the incumbent in 1992 (anybody remember Pat Buchanan's New Hampshire "surge?"). There is still opposition research to be done, commercials to air and many mistakes to be made.
Looking at this field, you have a great primary schedule and a lot of charisma in Edwards, a strong netroots following and national security credentials in Clark and charisma and experience in federal government and as an executive in Richardson. And that is only a few of the top contenders.
Anyone who tells you where this thing is going is being dishonest or is simply mistaken (I think the latter in Balz' case).