Here's a telling fact about modern American politics: Republicans only trust Fox News. Democrats trust every network but Fox News.

The numbers come from a new study from political scientists Matt Grossmann and Dave Hopkins collating five years of Public Policy Polling data on which major news networks people do and do not trust. PPP's data shows that Republicans are just as distrustful of mainstream outlets as of MSNBC, and Democrats are about as trusting:

PPP isn't alone in this finding. Grossmann and Hopkins survey a bevy of other sources finding similar patterns. A Pew survey found that the only outlets trusted by conservatives are Fox, the Wall Street Journal, Sean Hannity, Rush Limbaugh, Glenn Beck, Breitbart, the Drudge Report, and the Blaze, whereas liberals trusted both avowedly liberal outlets and mainstream ones that present themselves as neutral.

University of Texas professor Natalie Jomini Stroud's research has found that "conservatives allege and perceive media bias more often than liberals," while the University of Pennsylvania's Kathleen Jamieson and Joseph Capella found that "mistrust of the news media was especially high among talk radio listeners." Georgetown professor Jonathan Ladd conducted open-ended interviews with Republican voters on the media, and found that most cited concerns that the mainstream media is biased.

Grossmann and Hopkins are clear that these concerns have some basis. Academic research into media bias has found mixed results, but it's unquestionably true that most reporters are left of center, and big national outlets tend to be centered in urban areas, introducing some (largely unconscious) cultural biases that favor liberal cities and disfavor conservative rural areas.

Democrats "understate conservatives’ legitimate aversion to trusting mainstream media institutions often disproportionately staffed by non-conservatives to fairly adjudicate information on the public’s behalf," Grossmann and Hopkins write. And while Democrats don't prefer partisan media, the mainstream media they do consume "implicitly flatters the Democratic worldview."

But whatever the reason for conservatives' distrust of the media, Grossmann and Hopkins find it has huge implications for how Democrats and Republicans view politics.

Different media preferences lead to different kinds of political parties

Grossmann and Hopkins's broader argument is that Republicans' distrust of the mainstream media creates an asymmetry in how the parties approach the media. Democrats rely on the mainstream media both to get out their message and to cover events. Republicans generally distrust mainstream outlets and so have set up a parallel ecosystem to get their message out.

The result is Republicans rely on a media that is more likely to echo their partisan biases, and Democrats rely on media that does not pick a side and at least claims to be objective and empirical (whether or not it lives up to that promise). "Democrats therefore remain relatively unexposed to messages that encourage ideological self-identification or describe political conflict as reflecting the clash of two incompatible value systems," Grossmann and Hopkins write. "Instead, the information environment in which they reside claims to prize objectivity, empiricism, and policy expertise."

Of course, Democrats have their own left-of-center media. But it's not as tightly aligned with their party, and not as successful. The talk radio syndicate Air America was a colossal failure, and MSNBC lags behind Fox in viewership. "MSNBC is not nearly as important or as trusted a news source for liberals as FNC is among conservatives," Grossmann and Hopkins write. In a Pew survey, "Consistent conservatives overwhelmingly report trusting FNC (88 percent) and receiving at least some of their news from the network (84 percent), compared to 52 percent of consistent liberals who trust MSNBC and just 38 percent who watch it at least part of the time."

The result is a situation where Democrats gain most of their information, and build their worldviews, primarily on information from mainstream media sources not aligned with either party, whereas Republicans rely overwhelmingly on partisan media. This has real political consequences. Distrustful voters, Ladd writes, are "more resistant to new information and rely more on their predispositions when forming perceptions of the world around them. As a result, they heavily weigh their partisanship when voting."

Grossmann and Hopkins confirm this, citing a bevy of evidence demonstrating that increased access to only one side's media increases partisanship and ideological commitment in news consumers. The University of Pennsylvania's Matthew Levendusky experimentally exposed study participants to Fox and MSNBC, and concluded that "partisan media make citizens more convinced that their views are the ‘right’ one … make citizens less willing to trust the other party and less willing to support compromise with them, thereby contributing to persistent gridlock … [and] influence vote choice, as well as how citizens come to understand elections."

There's also good evidence that this kind of "selective exposure" is disproportionately powerful among Republicans. "One study found that adding the FNC logo to a news story increased the probability that Republicans would choose to read the story by 25 percentage points, whereas adding CNN’s logo or NPR’s logo reduced the chance by 10 points," Grossmann and Hopkins write. "No equally strong effects occurred among Democrats."

The core distinction: The GOP is an ideological party; the Democrats are a coalition

Grossmann and Hopkins's underlying explanation is that the Republican Party and the Democratic Party are fundamentally structurally distinct. Republicans are "chiefly defined by a common ideological commitment," while Democrats are a "coalition of social groups."

They marshal empirical evidence to back this up. They looked at Democratic and Republican guests' appearances on Meet the Press and found that "Democratic guests were more likely than Republicans to cite particular social or interest groups and referenced demographic groups more than twice as often. … Unlike Republicans, Democrats rarely use media appearances to articulate broader ideological principles."

They also look at data collected about op-ed columns by Georgetown political scientist (and Vox contributor) Hans Noel, and find that "conservative opinion columns are much more likely to mention (conservative) ideological principles whereas liberal columns are more likely to mention demographic groups."

So on the one side you have an ideologically rigorous party/movement that relies on its own newsgathering and information-producing services, leading to an increasingly distinct worldview from Democrats or independents.

"Today, the same patterns of information use and dissemination are repeated in every election and each policy dispute," Grossmann and Hopkins write, "producing a political conversation that is less a 'great debate' over principles and policies than an asymmetric dialogue between combatants who do not share each other’s rules or styles."

How this helps explain 2016

It's unclear how this analysis translates to 2016. On the one hand, the understanding of the Democratic Party as a set of interests perfectly explains why the candidate with broad demographic support and interest group loyalty (Hillary Clinton) beat the ideologically pure candidate who wanted to cleanse the party of its more rightward, pro–Wall Street elements (Bernie Sanders).

The Republican side is trickier. The theory helps explain why Marco Rubio and Jeb Bush were forced out; they were seen as ideologically untrustworthy, and in a predominantly ideological party that's not viable in a nominee. Ted Cruz's rise aligns well with the characterization of the party.

Donald Trump is trickier, given elite conservative media's (and Fox News's) disdain for his views on health care, foreign policy, and entitlements and his past views on abortion. He's also personally gone to war against Fox News, attacking Megyn Kelly for excessively tough debate questions and declining to appear at one January debate. Maybe his rise is a sign of the party getting less ideological and less tied to partisan media.

Then again, it could be saying something about what the ideology undergirding the party, from the point of view of its voters, really is. Whatever else can be said about him, Trump is more consistently anti-immigration and anti-Muslim refugee than any other candidate — positions that, while unpopular in much of the media, have often been embraced in conservative talk radio. It could be that rank-and-file conservatives view those positions, at this point in time, as more crucial than disagreements on health care or Social Security.

This would help explain why talk radio hosts like Michael Savage, Rush Limbaugh, and Sean Hannity are either pro-Trump or friendly toward him, even as Fox is skeptical. Maybe Republican primary voters aren't getting less rigorously conservative. Maybe they're telling us something about what they think conservatism really is.