Once upon a time — oh, about two presidential elections ago — Dianne Belsom would get up in the morning and read the paper, taking in news stories about candidates and campaigns. Some stuff she agreed with, some she didn’t.

This morning, Belsom wakes in her splendidly restored pink Victorian on Main Street in this rural South Carolina town, makes coffee and settles in at her desktop to fire up Facebook. There on her news feed are more than 100 stories that some of her 460 friends have posted since Belsom went to bed eight hours ago.

Over the next three hours, Belsom bops around the Web checking out the latest campaign news. Her sources are big and small, from nearby Greenville to faraway California, but they have one thing in common: With rare exceptions, the news and commentary sites Belsom visits share her worldview, which she describes as “conservative, tea party, Christian.”

She reads about why Ron Paul is out of step with conservatism at Commentary magazine’s site and Breitbart.tv. She takes in arguments about why Mitt Romney is too moderate at newsmax.com and Vision to America. And she nods firmly as she looks at comments from fellow Newt Gingrich supporters at teapartynation.com and the Washington Times site.

With just hours remaining before South Carolina’s Republican primary, it’s clear to campaign strategists and voters alike that the revolution in how Americans get their news has dramatically altered the political process. There’s more campaign news and commentary out there than ever before, but more and more citizens are tucking themselves inside information silos where they see mainly what they already agree with. The result, according to voters, campaign strategists and a raft of studies that track users’ news choices, is an electorate in which conservatives and liberals often have not only their own opinions but also their own sets of facts, making it harder than ever to approach common ground.

The audience is so polarized that even when consumers look for more entertaining sorts of news, such as travel or sports stories, they tend to choose sources that match their political leanings — conservatives to Fox News and liberals to National Public Radio, for example — according to a study by professors at Stanford and UCLA that dubbed this phenomenon “selective exposure.”

Forty miles away from Belsom’s book-lined study, James Akers Jr. joins nine members of his weekly breakfast club at Tommy’s Country Ham House in Greenville for a morning of happy yammering about politics and the joys (and tyranny) of Facebook and Twitter.

“We don’t need CNN anymore,” says Lee Ann Carter, who, like most of those at the table, met Akers on Facebook. “We have James’s Twitter.”

Akers, a 30-year-old real estate agent who is also vice chairman of Greenville County’s Democratic Party, is an incessant tweeter, the kind of guy who, if he wakes up at 3 a.m., checks his Twitter feed before he goes to the bathroom. At meals, friends have to order him to quit tweeting long enough to down some food.

What Akers recommends to his 798 followers on Twitter are news articles and commentaries, almost all from sites that fit comfortably with his socially liberal perspective — places such as MSNBC, Huffington Post, Mother Jones and CNN.

In conservative South Carolina, Akers finds that most of his friends are Republicans, even if he is a Democratic official. He considers it his job to try to convince his friends that they are wrong about many of their positions. But he has to be careful about the sources he uses: “One deal I have with my friends is that I can never use Huffington Post as a source because they don’t believe anything they read there. It’s just too liberal for them.”

Both Akers and Belsom realize that they have placed themselves in political echo chambers in which they mainly hear what they want to hear. But they say this is where they are comfortable.

“It really annoys me when people say something absolutely false, like how Obama’s a Muslim,” Akers says. “But we’re existing in completely different sets of facts, and you can’t get past that. All you can do is end the conversation.”

Belsom, who is 46 and home-schools her 14-year-old daughter, Desiree, has no qualms about steering her child toward sources that confirm the family’s view of what America is and should be. “I know that people tend to read the things they already agree with,” she says. “I’m not going to known liberal Web sites. But even if I wanted to look beyond what shows up on my Facebook page, I wouldn’t get to see that, because the way Facebook and Google work, they filter information according to where you’ve been before, so you just get more of that.”

Fragmented audience

Over the past decade, as Americans have shifted their attention from traditional news outlets to Web sites and social media, they have become harsher judges of the credibility of news outlets. Only “60 Minutes,” local TV news, NPR and Fox News have held their own in believability ratings, according to an extensive study by Pew Research Center of news consumption habits. Newspapers, network newscasts and some cable news channels saw sharp declines in credibility. Even C-SPAN suffered a loss of trust.

Although the vast majority of Americans still make the news part of their daily routine — 83 percent, according to Pew — how and where they get their news varies according to age, education, facility with new media and, increasingly, ideology.

About two-thirds of Fox News viewers are Christian conservatives, but only a quarter of those who watch “The Daily Show” or “The Colbert Report” fit that description, Pew found in 2010. Six in 10 CNN viewers call themselves progressives, compared with only a third of Wall Street Journal readers and a quarter of radio talk-show host Rush Limbaugh’s audience. Over the past decade, Republicans have listened to more talk radio as Democrats have watched more late-night topical comedy TV. Conservatives are more likely than liberals to read a daily newspaper, and liberals are more than twice as likely as conservatives to listen to NPR.

Fox, the only one of the three cable news outlets whose audience has grown sharply in recent years, has won over a strongly Republican audience: 40 percent of Americans who align with the party are regular Fox viewers.

The more clearly defined a voter’s political leanings, the more likely that person is to identify a few trusted news sources.

Moderates and independents are much more likely to view a relatively broad array of news outlets as trustworthy. And, according to surveys of news consumption, the less ideologically rigid voters are, the more likely they are to take in news that may not match their point of view.

Firm conservative, but . . .

At 23, Flynn McKinney is two years out of college, with a good job in human resources. She calls herself a firm conservative, but she is considering voting for Mitt Romney on Saturday even though she thinks he is a moderate.

McKinney is a news omnivore, and she does it old-school. She’s a perky sort, loves Clemson sports teams and has a robust network of friends. But she is nearly alone among them in paying for the online edition of the Greenville News, the local daily, which she never looks at in print. She and her husband, Clinton, have a daily ritual after work: They cook dinner and take it into the living room, where they watch the local news on Channel 4 and then “NBC Nightly News,” just like her parents did as she was growing up.

They also watch the candidate debates, one of the few media experiences that still reach across the ideological divide to gain a mass audience. This week in South Carolina, according to a new NBC poll, Romney led Gingrich by 15 percentage points before Monday’s debate, but Gingrich narrowed the gap to five points after his strong performance in the Fox News debate.

Unlike many religious conservatives, McKinney has little animosity toward the news media. She’s more likely to read — and trust — the New York Times or washingtonpost.com than she is the conservative blogs that rail against liberal media bias. She’s “very pro-life, very conservative on economic policy,” but she’s wary of the tea party, skeptical of the claims in candidates’ TV ads, and downright disgusted by how the candidates bash each other.

As the days until the primary ticked by, McKinney has struggled toward a decision. The ABC interview with Gingrich’s second ex-wife, in which she said he wanted an “open marriage,” slammed the door on voting for him. Now she’s “leaning toward Romney” but still open to Santorum.

“I am very fact-based,” she says. “My principles are set in stone, but I like to see two sides of any argument. I take the time to look up people’s voting records to see if I agree with them. My friends think that’s a little weird, but that’s how I make decisions. I want to see the full gamut.”

Leans left, but . . .

Akers is also a news junkie, but his constant screening of the latest bulletins takes place in a narrower space. On his Tweet Deck, a program that presents Akers with a rolling stream of messages and links from friends, colleagues, and reporters and pundits he likes, he sees an America that leans left, a place where same-sex marriage is a natural right and the government is not necessarily a force for evil.

“I’ll occasionally look at Fox, but I get so irritated, the way even in their news they make conservative comments,” he says.

But Akers was never so deep in his information bubble as to block out alternative ideas. Although he was a Hillary Clinton delegate at the last Democratic convention, he has been disappointed enough by Obama — “He’s become such a divisive figure” — to have fallen for Jon Huntsman, the Republican who Akers thought would be tough on spending but moderate on social issues.

Now that Huntsman has dropped out, Akers is weighing whether to risk expulsion from the county Democratic hierarchy if he votes in the GOP primary — in South Carolina, all voters may take part in any party’s primary — or stick with his own party.

He has been surprised to find himself interested in Romney as a moderate who might not be that different from Obama and might be more competent. And as his Democratic friends send him links to YouTube videos in which Ron Paul calls for steep cuts in military spending and supports legalizing same-sex marriage, Akers is intrigued.

By Thursday afternoon, he’s wavering between Romney and reluctantly sticking with Obama.

Akers hurries home to his snazzy condo, a fourth floor walk-up in a renovated building that was once a college dorm. He feeds the dogs and checks the latest tweets. He loves how the new world of social media keeps every day feeling urgent and alive, yet he sometimes wonders when he will just stop and breathe.

“The whole breaking news thing is so exciting, the chance to be right on the edge of everything,” he says. “But everything’s subjective, and you kind of have to figure out for yourself who’s right and what’s true. It can be hard.”

‘Christian worldview’

Across the political divide, Belsom, who supported Michele Bachmann before turning to Gingrich, agrees: “I try to avoid a lot of what the media puts out that is biased. But because I am mostly on Facebook and a lot of my friends are pro-Newt, it comes as a shock to me when I turn on the TV at a hotel — we don’t watch TV at home — and I see how pro-Romney the media are.”

Belsom — gracious, willowy and chatty — sometimes worries that she’s not seeing the full picture, yet she wants her family to live firmly in “our Christian worldview. I want my daughter to know that we are under attack by radical Islam, even if she sometimes gets depressed about the whole movement to Sharia law. I home-school her because the government schools have an anti-Christian worldview, so they’re teaching lies.”

Growing up in South Florida, Belsom read three local newspapers, and the family watched the evening news on TV. But as she and her parents grew more religious, they began reading mainly conservative and Christian outlets. The bookcases in Belsom’s home office include shelves of titles on creationism, as well as books warning against pornography, “the gay agenda” and radical Islam.

On Facebook, the big story is Obama deciding against approving an oil pipeline from Canada to Texas. Belsom scans rants against the decision. One headline reads, “Obama cans pipeline, signaling no interest in job creation”.

“I think we can all agree Obama’s driving us into the ground,” she says. “My honest opinion is that he hates our country and is trying to destroy us. Hopefully, I’m not too tunnel-visioned. But I guess I mostly see what I agree with.”