4) It is a new district. Switching Linn and Scott is a major shift. I don't think either would have a name ID issue in a primary, but whatever edge he'd have is gone. I think it's pretty ridiculous to say that someone named Vilsack would have a name ID issue in an Iowa Dem primary anyway. Additional counties Loebsack has never represented: Jasper, Marion, Mahaska, Keokuk, Clinton, Lucas, Monroe, Clarke and Decatur.
5) The nature of the party. The simple fact is that there are a lot more women in the Democratic Party than men. I don't think she makes gender a big issue, and shouldn't, but it will be a major deciding factor for a lot of people. Especially with the whole "Us and Mississippi" thing that everyone seems to be aware of.
6) Rural Dems. Which would you vote for if you were a rural Democrat? The wife of the current Ag Secretary or the liberal egghead Professor? Thought so.
7) Redistricting as cover. While some party people might be upset with her for running, the broader electorate doesn't view congressional seats as "belonging" to anyone. Additionally, since he will have to move into the district, she can say that she has just as much claim to it as he does. I personally tend to agree with these things on principle and I'm not alone.
8) She has a network. She has been on the political circuit for years now. She's done a ton of fundraisers for State House and Senate candidates and has a militantly loyal group of librarians all over the state (I kid you not, I've witnessed it over and over). I also know that shes been visiting USDA offices regularly as well.
I honestly don't have a dog in this fight. I don't live in the district currently and I think Loebsack has been a good progressive. He may not "deserve" to be primaried, but a lot of people don't view it that way. He inspires no passion from what I can tell and she does. That is big in a primary. It may not be "right" for her to run, but this is politics, not grade school. She has the ambition and a path to get there, so I think she'll do it. The only other eventuality I see is if she polls the new 4th and sees a path to victory there. Lastly, I think a primary might not be all that bad as far as getting the most Democratic part of our state activated in the run up to a general in which apathy may be an issue on our side.