Who wins, obviously, is the major question, followed shortly thereafter by which candidate feeds reporters the best grub. But there are other interesting subplots, in no particular order.
1. Tom Tancredo -- where he finishes, what he says.
2. Does Tommy Thompson finish second? If not, he's out.
3. The war of attrition between Sen. Sam Brownback and Ex-Gov. Mike Huckabee. Kansan and Arkansan. Catholic and Protestant. Comprehensive immigrationalist and comprehensive immigrationalist. In many ways, they're really quite similar. Based on anecdotes alone, the betting money is that Brownback has a better campaign organization and can expect, thanks to reliable stalwarts like pro-life activist Chuck Hurley, a solid turnout. But Huckabee has been working heavily Christian towns hard, and several Brownback rivals are spreading some tough (and arguably misleading) opposition research about him.
4. Newt Gingrich -- he'll have a booth in Ames, and everybody knows his name. It's hard to imagine how he plays a role, but he's Newt: you never know.
5. Romney v. Brownback -- Romney has finally begun to skirmish with Brownback on the margins, much to Brownback's delight and probably to Romney's chagrin. Have any of Brownback's criticism made a dent in Romney's support? If so, how will we know?
6. Rudy Giuliani -- remember, he's been on the air here recently with radio spots and just finished a multi-day tour. Mitt Romney has turned to a direct confrontation with Giuliani over recent days; the Giuliani team suspects it's because Romney does not want to be lumped in with the second and third tier candidates who are competing at Ames.
7. The Democrats -- how many times do the candidates mention Hillary Clinton (or Barack Obama) and what do they say? Do they trot out the old standards? Or have they refined their arguments?
8. Ron Paul... and this legal challenge. Apparently, the state party is using Diebold machines. And Ron Paul also wants them to count paper ballots.
9. Whether Mitt Romney pulls campaign manager Beth Myers aside and asks whether they _really_ had to spend _all_ this money? (To which Myers will reply: "Yes, Governor.") Ron Kaufman will then join the conversation and start by saying, "Look it, Governor..."
10. The presence of outside interests... Ed in '08 ... the Democratic state party ... the ONE campaign..... Redeem the Vote....
11. This one is for the media folks: which Iowa reporter becomes the next national superstar? (Yepsen, Zeleny, Glover, Beaumont are excluded.) My guess: O. Kay Henderson.
Marc Ambinder is an Atlantic contributing editor. He is also a senior contributor at Defense One, a contributing editor at GQ, and a regular contributor at The Week.