If NFL fans refuse to go to games until players stop disrespecting our Flag & Country, you will see change take place fast. Fire or suspend!

— Donald J. Trump (@realDonaldTrump) September 24, 2017

Should Trump’s supporters respond to that call, the medium-term effects could be serious for the NFL. But the impact would be at least as bad, and much more immediate, for the broadcasters who pay to air games.

The anthem protests, which began with former 49ers quarterback Colin Kaepernick and have now spread throughout the league, already appear to be affecting NFL ratings. Last week, with the 2017 season barely started, ratings were down a stunning 15% year over year, according to the Hollywood Reporter – and that’s after an 8% slide last year.

That has triggered an immediate slump in the stocks of broadcasters locked into NFL contracts, with some down as much as 9% this month. That includes ESPN owner Disney, NBC parent company Comcast (by far the worst hit), and CBS. A recent J.D. Power poll found that the anthem protests were the largest reason football fans tuned out, though it barely edged out other factors including cord-cutting, domestic abuse scandals, and weak matchups.

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But Trump’s tweets could make the protests an even bigger factor. Trump’s supporters have little sympathy for the issues being highlighted by the anthem protesters, expressing overwhelming opposition to the Black Lives Matter movement that helped inspire some of the players. Republicans have, in general, approved of some of Trump’s most racially divisive past comments, including his reaction to the deadly Charlottesville protest earlier this summer, according to a CBS poll.

The NFL itself, though, is insulated from those impacts by the long-term broadcast contracts, each worth between $1 billion and $2 billion per year, according to Forbes. The biggest deal, with ESPN, was signed way back in 2011, and runs through 2021. Deals with Fox, NBC, and CBS run through 2022.

NFL commissioner Roger Goodell has repeatedly defended his players’ right to free speech, and has called Trump’s most recent comments on the anthem protests “divisive.” Now team owners are lining up against Trump. History seems likely to vindicate their stance, much as it has the Brooklyn Dodgers’ decision to integrate baseball in 1947. And with nearly five years left to reverse the ratings slide before renegotiating its contracts, the league has the leverage to take the moral high ground.

The bigger question, though, is whether a Trump-led boycott would have the desired effect of silencing player protests — and that seems highly unlikely. With Goodell publicly supporting players, it would be left to teams, networks, or sponsors to pressure them to stop. Teams could cut vocal players — Kaepernick is already without a contract — though that situation is complex. But proactive moves to silence the protest would almost inevitably lead to a public relations disaster, particularly since the younger fans prized by teams and sponsors are more likely to support the protesters’ agenda. And Kaepernick’s gear has continued selling well even with him out of the league, arguably indicating that the most passionate fans are behind him and his allies.

So the likely outcome will be continued erosion in viewership, costing broadcasters hundreds of millions of dollars. That could impact renewal negotiations down the line, but even a divisive NFL remains a rare unifying force in an increasingly fragmented media landscape. And five years is a long, long time.