Republican
The one reason to listen, no, to sorta laugh with, Trump? He talks about his poll numbers. I don't believe he's any more poll-obsessed than any other politician. Obama spent more money on polls than any other candidate ever to win Iowa in 2008. Every position he took, every word he said, in Iowa, in 2008, was crafted with poll numbers to back it up.

It was an amazing draw: Millennial's were his base, liberals that were first-time caucus voters, and Republican-Independents. Trump is going to win Iowa with just about the exact inverse of that coalition. Think about it-- more middle aged, conservatives that don't bother to vote in caucuses, and dissafected Democrats. It's not going to be even close.
Trump- 40
Cruz- 25
Rubio-15
Paul-5
Carson-5
Others-10

If Rubio gets a late endorsement-bounce that will come out of Cruz to close the gap between the runner-ups. Paul might be a bit higher (I hope so) and Carson might be non-existent. Bush? If he doesn't get 5% he should just drop out and endorse someone in NH.

Democratic
Clinton's base of the elderly vote, along with an inevitable gender gap, makes her nearly impossible to beat in Iowa in a one-on-one contest. Sander's campaign does have shades of Dean, with his high College-area county numbers & vocal online progressive support. This reminds me a lot of Gore vs Bradley in 2000 though, and I expect, with a similar outcome.

Clinton- 55
Sanders-45

Clinton's also going to benefit from the caucus-style voting to award delegates. The delegate math is very difficult for Sanders. http://cookpolitical.com/story/9179
But Sanders has ran a great campaign, way better than I imagined. Their handling of the stupid forced-error by the DNC was stupendous.

I'll revisit this, before NH, but suffice to say that it could just be a repeat of the above on both sides.

A Trump vs Clinton election would be a good enough reason to tune out politics for the year. I am hoping its a bit more messy. If Sanders could pull off an upset in IA, he's got a great shot at keeping his advantage in NH. In NH, ARG looks like they may be picking up on a Kasich trend. I have been looking for someone that fits the Independent-swell slot. Especially if Clinton wins Iowa and looks safe, then Indys will be looking for a McCain-type. http://americanresearchgroup.com/pres2016/primary/rep/nhrep.html

Trump really needs Cruz to finish second in Iowa and NH. Kasich finishing 2nd in NH would derail Trump's steamroll.