The Trump administration released the first part of its proposed federal budget this morning, the third of the president’s term. The “blueprint” that came out today doesn’t include line-by-line funding requests for federal agencies; Bloomberg says that’s “expected later this month.” But when they do arrive, it’s expected that Trump will, for the third time, propose eliminating all federal funding for public broadcasting — zeroing out the Corporation for Public Broadcasting, the entity which then distributes those funds to support public radio and television stations.

He did it in 2017. He did it again in 2018. And both times he failed; the Republican-controlled Congress funded CPB anyway. Given that Democrats now control the House, the chances of Trump getting his way on Take 3 are even more remote.

Why has Congress protected Big Bird so far? Or, to put it another way: Why have two branches of government controlled by the same party treated funding for public media so differently?

There are a few reasons. A presidential budget is essentially a messaging tool these days, a way to show your supporters that you’re addressing their priorities; Congress has to actually decide where real money will go. Just about every member of Congress has a public radio or TV station in his or her district; any transition from rhetoric to reality would be felt back home. But it’s also because public broadcasting is actually pretty popular and pretty trusted by Americans.

Last month, PBS ranked as the most trusted American institution for the 16th straight year. (It’s a PBS-sponsored survey, but other evidence backs that up.) A 2014 Pew study found that, among 36 national news organizations, NPR and PBS finished No. 3 and No. 4 in a ranking of the most trusted; a 2017 Mizzou study ranked them No. 5 and No. 6 of 28 major news outlets.

That’s trust — what about bias? A Knight-Gallup survey last year found that, of 17 news organizations, PBS and NPR ranked No. 1 and No. 2 in the number of people who said they are “not biased at all.” And while Democrats saw less bias in them than Republicans did — something that’s true of nearly all mainstream news outlets — Republicans consider them nowhere near the worst offenders, ranking PBS 5th and NPR 9th.

So Trump’s annual CPB cut is Kabuki theater that doesn’t really threaten funding for public broadcasting. But I do worry about the long-term impact of this annual dance. There’s a large body of political science research that shows public opinion on a given issue varies depending on how closely attached it is to people’s partisan identities — and each “statement” budget strengthens public media’s attachment a little bit more.

Let’s say you asked a group of conservatives and liberals about a subject — let’s call it Policy X. Then imagine you asked a similar, second group about the same subject, but this time adding partisan context: “Barack Obama strongly supports Policy X. Donald Trump strongly opposes Policy X.” Even if those two groups walked into the room with exactly identical views, you’ll get different responses — because the second one has been primed to view the issue through a partisan lens. If they know what the “correct” position is for the political team they identify with, they’re more likely to support it. (Philip Converse called this knowing “what goes with what.”)

For example, it used to be that both conservatives and liberals thought that colleges and universities have a generally positive effect on society. It wasn’t a particularly partisan or ideological issue. But as colleges became more salient as a political issue — being drawn increasingly into culture-war issues and described as home to out-of-touch elites by conservative media — Republicans flipped. In 2015, 54 percent of Republicans and 70 percent of Democrats thought higher education was a positive influence. But by 2017, Republican support had collapsed to only 36 percent. (Democrats were steady at 72 percent.)

So every time Trump slices CPB out of a budget, he raises the political salience of public broadcasting as an issue. It encourages people to think of PBS and NPR as “Republicans” and “Democrats,” not “single mom who likes letting her kid watch PBS Kids,” or “parent who likes PBS education programming,” or “suburban dad who’s a little too into Wait, Wait…Don’t Tell Me!,” or “commuter who finds Morning Edition the only tolerable thing on the dial.” Public media has always, to varying degrees, been a partisan issue, dating back to the days Richard Nixon tried to kill it. But in today’s era of extreme political polarization, encouraging people to think of something as partisans rather than users drives a lot of them to their political corner. The best thing that could happen to NPR and PBS would be to be treated as boring, a utility.

Remember that PBS-sponsored survey that found public TV was America’s most-trusted institution for the 16th year running? It’s true: 29 percent of people surveyed said they trust PBS “a great deal,” more than the court system (17 percent), digital platforms (15 percent), commercial cable TV (14 percent), and commercial broadcast TV (12 percent).

But take a look at how that “trust a great deal” number has moved, before and after Trump started running for office:

2013: 46%
2014: 42%
2015: 48%
2016: 36%
2017: 42%
2018: 30%
2019: 29%

That’s the sort of trendline that you’d see if more Americans were seeing public broadcasting through an ideological lens instead of a civic or user-driven one. And even if Trump’s budgets don’t impact policy, they contribute to shifts in public opinion that someday could.