Let me say this right off the bat - you're a top-notch candidate. Any other year, any other primary, any other opponent, and you'd be sailing to the nomination. But you're a better candidate than your campaign, and it's time for you to withdraw gracefully.
Oh, and if you could do it on March 7th, that would totally rock - it's the day I predicted to my students that you'd withdraw.
Let me give you the brief rundown before going into detail - your opponent has better on-the-ground organization, he fundraises like no candidate ever has (and without the desperate-sounding e-mails I get from your campaign), his rallies pack massive stadiums while yours leave empty seats at amateur hockey rinks, and your main line of criticism not only falls flat but boomerangs. As Eugene Robinson noted, if your situations were reversed, there would be daily calls for Senator Obama to step aside. And those making the calls would be absolutely right to do so.
On the issue of campaign organization, it's clear that you weren't prepared for an extended post-Super Tuesday contest - financially or managerially. A well-run campaign doesn't question the significance of nearly half the states. A well-run campaign invests the (relatively small) resources necessary to learn how the Texas hybrid system works and field a full slate of delegates in Pennsylvania - two states that will certainly prove their significance in the coming weeks. I might (might) overlook these sorts of oversights if you were running on a shoe-string budget, but you've spent well over $100 million to make the kind of errors any freshman Political Science major would giggle at. These are the opportunity costs of $100,000 of meat-and-cheese platters (to be fair, you may have also invested in fruit trays - I'm just an amateur observer).
You're blowing through cash like a 40-horsepower LeafMaster9000, but look at the bright side - you aren't raising nearly as much as your opponent. While you're sending me desperate e-mails, Senator Obama raised more than you, Senator McCain and Governor Huckabee combined in January and could be well on his way to raising $60 million in February alone. You're thinking about how many cleaning bills you could skip out on with $60 million, aren't you? Senator Clinton, please - I need you to concentrate. Senator Obama isn't only raising an unprecedented amount of money in a primary, he's doing it by convincing people like me to brownbag it for a week so we have an extra $25.01 for his campaign. He certainly isn't pushing nine out of every ten donors to their federal maximum!
I don't know how much it costs to hire a goth band (or, frankly, why anyone would pay pale teenagers dressed in black to whine at them), but if it fills arenas, then your money is well-spent. I think more people than Jose Bustos were expecting a little more. Although maybe they shouldn't have been surprised at the low turnout, since you're polling more points behind Senator Obama than asterisk-candidate Mike Huckabee is behind McCain. Senator Obama not only fills the home of the UW Badger basketball team past capacity ("We're risking the fire marshal's wrath for change!"), but has such a draw that tens of thousands are willing to wait outside for hours in negative-windchill temperatures for the opportunity to cheer for him. If you withdraw soon and ask politely, I bet you can still get a good seat at Citizen's Bank Park for the pre-Pennsylvania rally.
Finally, you've been critical of what you perceive as a lack of experience from Senator Obama. I realize you're busy, but maybe one of your highly-paid staffers could give this a quick read. It's daunting, I know - but I'm sure you wouldn't want your campaign to be misleading? Right? After all, your cries of plagiarism just before my state's primary not only failed to sway my fellow cheeseheads, the negativity may have actually hurt you! We're shockingly polite here - not quite Minnesota nice, but certainly a close second - it's natural that you'd underestimate us. I hope you learned you lesson when the same line of attack earned you boos in Texas. (Also, I hate to point this out when you're in such a delicate position already, but you're a little bit of a hypocrite, Hillary! I'm sure John's line was just so good that it stayed with you, so I hope Howard Wolfson will be e-mailing me an update soon!)
Senator Clinton, now is the time to gracefully withdraw from this race. Wait, I mean March 7th is the time to gracefully withdraw from this race.