So why is that information important for a site that’s about politics? In a word: advertising. Broadcast television advertising is still one of the main expenses for a political campaign for federal or statewide offices. It’s certainly true that one of the takeaways from the 2016 election that people actually seem to be learning is that TV is a whole lot of money for not a lot of persuasion, and future campaigns might be interested in more emphasis on in-person get-out-the-vote and digital media. However, don’t expect broadcast advertising to entirely go the way of the Edsel any time soon.
Television remains an effective, even if an expensive, way to reach voters, especially older voters who tend to turn out in disproportionate numbers in non-presidential years. And live sporting events, which most fans still watch on television, remain particularly enticing to advertisers, since people are less apt to record them and fast-forward through the ads. (Note that cable TV advertising is a different beast: It can be significantly cheaper and more narrowly targeted, but that’s because it reaches fewer people.)
Ad rates, of course, are anything but uniform around the nation; they’re much more expensive in markets with more eyeballs, with New York City, the largest market in the nation, being the priciest. A campaign in an expensive market will necessarily make a lot of different strategic decisions than one in a cheap market.
Pop open the spreadsheet for a few examples concerning potentially competitive House districts next year. Indiana’s 2nd Congressional District is a prime example of a district where it’s really efficient to advertise on broadcast TV. If you look at the CD-to-DMA tab, you’ll see that 83 percent of IN-02 is in the South Bend media market. (There are also small bits of it in the Chicago, Fort Wayne, and Indianapolis markets, but those segments aren’t large enough that you’d want to advertise there—more on that in a moment.)
Conversely, if you look at the DMA-to-CD tab, you’ll see that 67 percent of the South Bend market (which is just the 96th-largest in the country), is in IN-02, with the rest in IN-03 and MI-06. That means you don’t have much of a “wasted eyeball” problem. In other words, you aren’t spending a lot of money to show your ads to people who live in a different district or a different state and wouldn’t get to vote for you even if they were interested. This is also why, incidentally, you wouldn’t want to advertise in Chicago to reach voters in IN-02: Only 7 percent of the district’s population is covered by Chicago TV, and it's also the third-largest market in the nation (and thus one of the most costly).
By contrast, take a look at New Jersey’s 3rd District, which stretches from the Philadelphia suburbs to the Jersey Shore. But while it’s close to Philly, it’s also close to New York City. In fact, NJ-03 is divided pretty evenly: 43 percent of its population is in the New York City media market and 57 percent is in Philadelphia, two of the most expensive markets in the country, again because of how many people they each contain. If you only advertise in one of the two, you’ll fail to reach around half of your district’s voters.
But no matter what you choose, you’re also going to be spending a lot of money to reach a lot of people who definitely can’t vote for you. The New York market is so enormous that it covers all or part of no fewer than 34 different congressional districts, and only 1.5 percent of that market lives in NJ-03. That means a candidate there who advertises in New York will be blowing cash on ads that’ll be seen as far away as Long Island or Connecticut. A similar phenomenon is likewise true with Philadelphia, as only 5 percent of residents in that market are in NJ-03.
That’s why this is one of the most expensive House districts to run in, and it’s no accident that the current incumbent, Republican Rep. Tom MacArthur, is a wealthy self-funder who’s worth at least $30 million. The alternative for a challenger who isn’t a multi-millionaire is to focus on cheaper forms of voter communication, such as mail, digital advertising, and cable TV.