LOL! (Sorry - I shouldn't laugh) Oh, wow. In terms of average temperatures, the daily *high* in Iowa gets up to around freezing. Check out the chart at this link:
http://countrystudies.us/united-states/weather/iowa/des-moines.htm
My suggestion is to make sure you have a hat that covers your ears, and a decent pair of insulated gloves. Iowa can be kinda/sorta gusty in midwinter, and wind chills are a real bitch. It's not unreasonable to worry about frostbite if the temp is well below freezing and the wind picks up. Be sure to have a couple pair of heavy socks to help keep your feet insulated. As far as coats or jackets, I would recommend "layering" with a T-shirt/undershirt with a heavier shirt (or better, a sweater or sweatshirt) and a good insulated windbreaker over that.
Just make sure you have at least one coat or jacket that is impermeable to wind. As weird as this sounds, you'll be a lot colder at 32 degrees and a fifteen mph wind than if the temperature is 15 degrees and the air is dead calm.
If you can't find cold weather stuff (Thinsulate gloves, etc) where you live, you might consider ordering over the internet. (There are a zillion good sites; campmor.com, cabellas.com, basspro.com, carhartt.com and rei.com just to name a few) Better still, if you know you'll have some sort of access to transportation when you get to Iowa, there are plenty of stores there that will have hats, insulated gloves, etc.
But I'm making it sound scarier than it is. I doubt the campaign is going to keep anyone outside on a door knocking death march. And there are a lot of good folks in Iowa. I wouldn't be surprised of you get some offers of coffee or hot chocolate!