In recent weeks, news anchors at local TV stations across the country have warned Americans about the “sharing of biased and false news” and the threat “fake stories” pose to democracy. As a recent video revealed, reporters recited word for word the same script bearing this warning.

What do these stations have in common? They’re all owned by Sinclair Broadcast Group, the largest television station conglomerate in the United States.

Critics have claimed that Sinclair — a company with close ties to the Trump administration and conservative politicians — is pushing its stations away from local coverage and toward a partisan brand of political reporting on national politics.

In new research, we find evidence that that appears to be the case. Stations bought by Sinclair reduce coverage of local politics, increase national coverage and move the ideological tone of coverage in a conservative direction relative to other stations operating in the same market.

Here’s how we did our research

Our research analyzes local news broadcasts across the country, comparing Sinclair-owned stations’ coverage patterns to those of other stations in the same market — and, when Sinclair acquires a new station, comparing how Sinclair ownership changes coverage patterns.

To conduct our research, we collected local news broadcasts’ ratings data and transcripts from every station in the country that had such a broadcast from mid-2017 to early 2018. (And, yes, this involved millions of transcripts.) During this period, Sinclair acquired 14 stations in 10 markets, increasing its portfolio to 193 stations in 89 markets across the country.

We run the transcripts through statistical software that determines how much of a broadcast is spent on each general topic, such as local politics, national politics, crime and weather. We also measure the ideological slant of the national politics coverage by comparing it to commonly used partisan phrases in the Congressional Record. Finally, we look at Nielsen viewership estimates for each 30-minute show in the data.

For the stations that Sinclair bought during this time, we estimate how Sinclair’s purchase changed a station’s content by comparing before and after coverage patterns relative to the changes at other stations in the same market and time period.

Here’s what we found. Compared with other stations in the same market, once Sinclair buys a station, that station

  1. Increases its coverage of national politics by roughly 25 percent,
  2. Decreases its coverage of local politics by roughly 10 percent,
  3. Shifts significantly rightward in its coverage’s ideological slant, and
  4. Loses a very small share of its viewers.

Existing Sinclair-owned stations cover significantly more national politics and have right-leaning slant, relative to the region’s general ideological disposition. In other words, Sinclair stations in D.C. are more right-leaning than other stations in Washington, and Sinclair stations in Butte, Mont., are more right-leaning than other Butte stations.

Local news and national politics

Local TV news remains one of the most important sources of news for many Americans. More than 25 million viewers watch local news each night — a substantially larger audience than watch national cable TV news like MSNBC or Fox.

In fact, with the collapse of the print news industry, local TV news may be one of the few remaining reliable sources of local news coverage. Political scientist Erik Peterson, for instance, documents a 28 percent average decline in local newsroom staffs from 2004 to 2014.

That coincides with an increasing nationalization of politics at the local level. In a forthcoming book, political scientist Dan Hopkins describes how the nationalization of politics has caused audiences to pay less attention to local news and more to news about national politics.

Our research, however, suggests that local TV news audiences are still seeking local news.

When Sinclair acquires a station and increases its national coverage, those stations lose a few hundred viewers, on average. In other words, there’s no evidence that Sinclair changes its focus in response to demand for more national news.

That’s not much of a ratings drop, of course, and local news is more expensive to cover.  By replacing local coverage with pre-written national politics segments, which Sinclair distributes to all its affiliates, stations no longer have to devote resources to costly local reporting. From Sinclair’s point of view, then, cutting local coverage may make economic sense.

But these trends have worrying implications, given what political scientists know about how political news coverage affects its viewers.

The importance of local news

Once Sinclair takes over a station, millions of Americans are exposed to a more politicized, right-leaning news broadcast with less local coverage every night.

In existing research, political scientists Greg Martin and Ari Yurukoglu have shown increased exposure to politicized cable news broadcasts leaves viewers more politically polarized and more likely to vote for the party aligned with the bias of the news broadcast. Local news may well have the same effect.

Further, research by political scientists Danny Hayes and Jennifer Lawless finds that when local newspapers disappear, communities know less about local politics — and are less likely to vote.

There’s already a dismally low level of knowledge about local politics and voting in local elections. If Sinclair continues to grow and changes its stations’ coverage in the ways we document in our research, citizens may lose their chances to hold elected officials accountable.

Gregory J. Martin is an assistant professor of political science at Emory University. Find him on Twitter @gregmartinphd.

Joshua McCrain is a graduate student in political science at Emory University. Find him on Twitter @joshmccrain.