BOSTON (CBS) – A warning for the Democratic presidential hopefuls ahead of tomorrow night’s debate – watch your language.

ABC, the network broadcasting the event, and the Democratic National Committee note the debate will not be on a delay, and is the first primary debate to be broadcast on an over-the-air network rather than cable, thus rendering profanity a violation of FCC rules.

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Why do they even have to say this?

Because open cursing has become a staple of modern-day political discourse.

It can be relatively tame, like the moment in a 2016 Democratic debate when Bernie Sanders told Hillary Clinton “the American people are sick and tired of hearing about your damn emails.”

Or it can be unsuitable for polite company, like a recent remark by Trump challenger Joe Walsh condemning a Republican Party move to cancel some of its primaries and caucuses as “absolute undemocratic bull—-.”

There’s nothing new about politicians cursing, at least, behind closed doors.

But as recently as 2004, when President George W. Bush and Vice President Dick Cheney were picked up on a live mic disparaging a reporter as a “major league —hole;” and in 2010, when Vice President Joe Biden celebrated the passage of Obamacare by telling President Barack Obama – within range of a live mic – that “this is a big f—ing deal,” it was considered unseemly when profanity went public.

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But, apparently, not anymore.

Consider some of 2016 candidate Donald Trump’s greatest campaign trail hits:

“The Democrats have to decide whether they will continue defrauding the public with ridiculous bull—-“…”Would I approve waterboarding? You bet your ass I’d approve it, you bet your ass.”

His crowds loves it, and Trump’s success in discarding the profanity taboo has spawned imitators.

For Beto O’Rourke, crass language isn’t a bug, it’s a feature, right down to the f-bomb-laden t-shirts his online campaign store sells.

No wonder those network executives are so worried about Thursday night’s debate.

So is there a price to be paid for public political cursing?

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The president’s abysmal character ratings might suggest there is. And while curse words are often good for an easy laugh from the crowd, maybe the late Mormon Church leader Spencer Kimball was on to something when he said: “profanity is the effort of a feeble brain to express itself forcibly.”