The Colin Kaepernick-led player protests may be hurting the NFL broadcast networks where its hurts them the most: in the pocketbook.

With NFL TV ratings plunging by double-digits over the first quarter of the 2016 season, some NFL TV networks are being forced to provide so-called "make-goods" to advertisers, media sources tell Sporting News.

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When advertisers and ad agencies buy commercial time on NFL partner TV networks, they're promised certain numbers in terms of ratings and audiences. If the game fails to reach those numbers, the networks have to "make good" for the audience shortfall by providing the equivalent of free commercial time.

The last thing TV networks want to do is give back valuable commercial time, especially when ad rates for a 30-second TV commercials during NFL games cost anywhere from $500,000 to $600,000 for prime time games on Madison Avenue.

But if NFL TV ratings continue to fall, it could cost the league's partner networks — CBS, NBC, Fox, ESPN and NFL Network — millions worth of make-good ads.

NFL game programming is the most expensive programming on TV, with CBS, NBC, Fox and ESPN paying a combined $5 billion per year for the right to air games through 2021.

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You can't blame it all on Kaepernick: Numerous factors are driving NFL TV ratings down this season, say sports media experts.

The U.S. presidential election between Donald Trump and Hillary Clinton is luring viewers to news channels like Fox and CNN, away from sport TV (This Sunday's presidential debate between Trump and Clinton will again cut into ratings for the Sunday Night Football game between the Giants and Packers).

The NFL has also been missing three star quarterbacks who've attracted national audiences in the past: the retired Peyton Manning, the suspended Tom Brady (who returns on Sunday) and the injured Tony Romo.

Viewers also have their pick of a glut of pro and college football to view. The quality of play is down this year, with many prime-time games turning into snooze-fests because of poor play, lopsided scores and questionable officiating.

It's also possible that the damage done to Brady's image from Deflategate — plus Ray Rice knocking out his fiancee and other scandals — may be finally catching up to the Teflon NFL.

Rather than blaming Kaepernick, Jason Whitlock of FS1's "Speak for Yourself" blames a "hyper-progressive movement that has lurched into sports — and changed the conversation about sports."

.@WhitlockJason blames progressive sports media for undermining interest in sports and the NFL rating decline. pic.twitter.com/XqAcqYEOq9 — Speak For Yourself (@SFY) October 5, 2016

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But you can't discount the impact from Kaepernick and protesting players either. Enraged by these protests, a small but vocal online group is urging millions of football fans to #BoycottNFL. A Rasmussen poll found 32% of adults are less likely to watch games due the Kaepernick-led player protests.

Some of these fans are angry at Kaepernick for politicizing sports, viewing it as the last refuge from political correctness and the Culture Wars. Others see the protests as an insult to police officers, members of the U.S. military and family whose loved ones have died in the line of duty.

There's something else at work here, too.

After decades of watching the NFL market itself as a paragon of patriotism, some fans feel betrayed by the league's passive acceptance of players refusing to salute the flag — while uniformed members of the police and armed forces stand at attention a few feet away.

The #BoycottNFL crowd is also going after league sponsors such as Budweiser, which pay billions annually to associate their brands with the NFL shield.

#BoycottNFL. You support an organization that does not stand for the National Anthem so we won't stand for Bud Light or the NFL ratings down https://t.co/PKrTgi5n7M — David Owens (@drowensdo1) October 6, 2016

These people have got to be kidding, counter critics of the #BoycottNFL movement.

It's pretty hypocritical to get up in arms about Kaepernick and other players exercising their right to peacefully protest, they say, especially when these same fans stuck by the NFL through far more serious scandals.

I said yesterday I'll say it again, if Kap makes you cut off the TV when domestic violence didn't, you're the one with the problem. https://t.co/KUXDxTANQm — MTCWithMook (@MTCwithMook) October 6, 2016

As Bleacher Report's Mike Freeman tweeted:

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The NFL was once thought to be immune from the ratings vagaries plaguing other sports. But the league's formerly bulletproof aura is taking a dent this year.

The league's overall TV ratings are down 10 percent, as reported by Joe Flint of the Wall Street Journal, citing data from Nielsen. The numbers are worse for primetime games on Sunday, Monday and Thursday nights.

Rating for NBC's "Sunday Night Football," America's top prime-time show for five years running, are also down 10 percent, as reported by John Ourand and Austin Karp of SportsBusiness Daily.

CBS' "Thursday Night Football" numbers are off 15 percent. ESPN's "Monday Night Football" ratings are down a whopping 19 percent.

The 2016 NFL season is still young, however, and one Madison Avenue expert predicts the NFL's TV ratings will bounce back after Election Day.

"It's a confluence of a lot of things. You've got an abundance of football on the air. Between college and pros, there's a lot of football. Some of the games haven't been that competitive. Maybe younger people are going away a little bit from television. And the election has turned people's attention way from football," said media buyer Andy Donchin of Amplify US. "But the NFL is the NFL. I really do think the ratings are going to come back."