Districts in Iowa (click here) tend to be competitive due to strong laws against gerrymandering.
By law, the nonpartisan state agency responsible for redistricting must
draw districts that are square, rectangular, or hexagonal and match
city and county boundaries as much as possible. The agency cannot
consider voter registration records and previous election results in the
process. In 2012, the state's four congressional seats were split
evenly between the two parties, with no candidates winning more than 60
percent of the vote.