Iowa's 1st Congressional District covers northeast Iowa, and includes the cities of Cedar Rapids, Dubuque and Waterloo.
Republican Rod Blum and Democrat Pat Murphy are neck-and-neck for the open seat, vacated by Democrat Bruce Braley who is running for U.S. Senate.
Click on a county to see population and voter registration information. Counties in red have more Republican voters than Democrats or independents, blue have more Democrats and yellow more independents.
In an email Democratic strategist Jeff Link points out while Republicans outnumber Democrats in more counties in the district, the counties with the bigger populations lean Democratic.
"Linn, Black Hawk and Dubuque counties all give the Democrats about a 10,000 vote advantage," writes Link, "which more than offsets the rural counties Republicans skew."
Also over email, Republican strategist David Kochel says the district, though traditionally Democratic, can vote Republican in non-presidential elections.
"Governor Branstad has carried every single county in this district," writes Kochel. "Pro-life Catholic Democrats in Dubuque County have long been a part of the GOP coalition, and Congressman Braley has struggled in polling in this district with low favorability stemming from his tenure in Congress."