Forget Fink winning outright, I'm happy if she keeps it within R+7 and consequently one of the congressional districts flip. Grassley or not the R-gains with WWC independents in the state is just too high and it's not WI/MI where Ds have made inroads to offset those losses.
The Iowa problem is an interesting one, because the suburbs were already pretty blue even before Trump. There's just not much space to gain.
On the other hand, urban cores weren't much bluer than the suburbs at that time either. Iowa circa 2012 really had a remarkable lack of geographic polarization.