By Adam Geller, AP National Writer

When a South Carolina congressman shouted "You lie!" during a speech by President Barack Obama in 2009, House members rebuked him for violating norms of civility. After this year's presidential campaign, the idea that people were once troubled by the outburst seems almost quaint.

Civility in politics has been declining for years, both a cause and symptom of a changing culture where anonymous verbal assaults are fired freely across the internet, and cable TV routinely broadcasts words once banned from the airwaves. But Donald Trump's presidential run took name-calling and mockery — things that voters long said they detested in their candidates — and normalized them into a winning political strategy.

Now Trump, the president-elect, is calling for unity in words that draw attention precisely because they sound so unlike Trump, the candidate. But many question whether it is possible to reverse the campaign's damage to political discourse and its ripples out to the way Americans speak to and about each other.

"There's plenty of blame to go around on this subject, but I think in this particular election that an embrace of Donald Trump was an embrace of incivility and vulgarity and insults and bullying, and unfortunately we saw very little public repudiation of that from any Trump supporters," said Mark DeMoss, an Atlanta public relations executive and conservative Republican whose clients are mostly Christian religious organizations.

DeMoss, who abandoned a campaign called the Civility Project in early 2011 after only three members of Congress would sign a pledge to act respectfully, watched the degradation of political speech for years. Then Trump's campaign, he and other longtime observers say, stomped well past what was thought to be acceptable.

"We can all point to incidents in campaigns across history, but I think this one probably does represent a new place in terms of incivility," said James Mullen, president of Allegheny College in Meadville, Pennsylvania, which awards a prize each year for civility in public life.

"What worries me the most is we're becoming almost numb," Mullen said.

When Allegheny — which first polled Americans about political civility in 2010 — did so again in October, researchers noted a "disturbing" decline in those rejecting insults in politics. The number who disapprove of political comments about someone's race or ethnicity declined from 89 percent to 69 percent. The number who said it was unacceptable to shout over a debate opponent fell from 86 percent to 65 percent.

Many observers blame Trump, who called Mexican immigrants "rapists," tarred his adversaries as "Lyin' Ted" and "Crooked Hillary" and complained that a TV journalist's dogged questioning was just a sign she had "blood coming out of her wherever." He said all of those things, not on long-forgotten tapes, but in front of millions of voters.

At Trump's rallies, supporters followed suit, chanting "Lock Her Up!" about Clinton and wearing T-shirts with the slogan, "Trump That Bitch!"

In some ways, Trump's rhetoric is an outgrowth of cultural and political shifts.

A generation before the internet, political backers were leaving fliers attacking rivals on voters' windshields in the dark and blanketing neighborhoods with anonymous direct mailings. Social media made it possible for ordinary people to disparage political enemies widely with no risk, saying things they might previously have told only their close friends.

"Into that world comes a candidate who uses Twitter as a primary mode of communication," said Kathleen Hall Jamieson, a professor at the University of Pennsylvania who studies political communication. "He lives in a world in which this stuff is being trafficked back and forth, and that normalizes this kind of discourse for you as a candidate."

But with their words, Trump, Clinton and other politicians set the tone for a much larger conversation.

Nearly 2,000 teachers surveyed by the Southern Poverty Law Center this spring reported that the campaign's scorching words were having a "profoundly negative impact" on their students. More than half said they had seen an increase in bullying, harassment and intimidation of students whose race, religion or nationality had been targeted by political rhetoric.

The survey did not identify any candidates. But teachers singled out Trump in more than 1,000 comments, while fewer than 200 combined named Clinton, Texas Sen. Ted Cruz, or Vermont Sen. Bernie Sanders.

In recent years, teachers mindful of bullying and taunts on social media have worked to make schools places of mutual respect, said Maureen Costello, director of the SPLC's Teaching Tolerance project.

"What made this year really different is that it broke through that protective moat," Costello said. The political rhetoric was "so ubiquitous and so saturated the culture that you couldn't keep it out of schools. Kids are sponges."

When Beth Ferris, a middle school teacher in Yucca Valley, California, told students on Election Day that history would be made one way or the other, one of her students said, "Yeah, she (Clinton) should be in jail!" At a nearby high school, vandals painted "Trump 2016," on a wall and covered the word "Girls" on a bathroom door with a vulgarity.

"I think it's going to get worse before it gets better," Ferris said.

On the day after the election, teacher Dee Burek said fifth and sixth graders in her Allentown, New Jersey, middle school asked how Trump had become the Republican nominee. She recalled his insults of opponents in debates and how they stuck.

"The kids just kind of looked at me and said, 'But that doesn't make any sense. That's bullying,'" she said. "If these middle schoolers can see that, I think there's hope."

Adults, who heard the candidates out and voted, have conflicted feelings.

"There were some things that were said about Hillary, that she should just go to jail and she should be hung, they make it sound so — it can't be that bad," said Byron Dopkins, an accountant in River Falls, Wisconsin, who voted for Trump. "What makes it worse (for) the public is that we can't have conversations with friends who are on the other side of the aisle without it getting nasty."

Still, Dopkins said one of the reasons he voted for Trump is that he is a "straight talker."

But that talk feeds a public conversation that leaves Melinda St. Clair, an Episcopal priest in Billings, Montana, who voted for Clinton, deeply troubled.

"I don't use the term 'civil discourse.' I don't think there is any," St. Clair said.

"I don't think we're listening to God. I don't think we're listening to each other. I think we're just hearing what makes us feel good at the moment and shouting it at the top of our lungs."

To Learn More:

As Nominee, Trump Employs Code Words to Fuel Racial Animosity, Say Observers (by Russell Contreras and Jesse J. Holland, Associated Press)

78% of Americans, Including Most Republicans, Say Rudeness Characterizes GOP Presidential Contest (by Laurie Kellman and Emily Swanson, Associated Press)

Twitter Still Trump’s Favorite Tool for Fear Mongering and Character Assassination (by Alexander Burns and Maggie Haberman, New York Times)

Trump Anti-Immigrant Rhetoric Emboldens Hate Mongers (by Noel Brinkerhoff, AllGov)