A remarkable year-long study by the Pew Research Center finds that what's trending on Twitter, often used by national reporters to gauge immediate public opinion of news events like President Obama's election, exaggerates to the point of lying.

The key reason: a majority of those who tweet are young Democrats, giving the social network an unbalanced view of the world. What's more: reaction is more negative than what public polls find.

Take the reception to Obama's reelection as an example. Pew said polling found that 52 percent of the public was "happy," and 45 percent "unhappy." But the Twitter reaction was 77 percent "happy," 23 percent "unhappy."

But there are times when the "Twitter universe" turns negative, even conservative. Here Pew offers the reaction to Obama's second Inaugural Address. Polling found that 48 percent had a positive view of it, 22 percent a negative view. But on Twitter, 66 percent were neutral, 13 percent positive, and 21 percent negative.

Twitter is huge in Washington, a place where reporters, lawmakers and lobbyists put news and get their information, giving it an outsized influence in the national debate.

But Pew found that Washington is a rarity: Most don't use Twitter. "Just 13 percent of adults said they ever use Twitter or read Twitter messages; only 3 percent said they regularly or sometimes tweet or retweet news or news headlines on Twitter."

And while some public figures like Republican National Committee Chairman Reince Priebus say they get their news from Twitter, the tweeting public leans Democratic. Said Pew:

"Twitter users are not representative of the public. Most notably, Twitter users are considerably younger than the general public and more likely to be Democrats or lean toward the Democratic Party. In the 2012 news consumption survey, half (50 percent) of adults who said they posted news on Twitter were younger than 30, compared with 23 percent of all adults. And 57 percent of those who posted news on Twitter were either Democrats or leaned Democratic, compared with 46 percent of the general public."