Chris Hughes, a co-founder of Facebook and an organizer of Barack Obama’s 2008 presidential campaign, has purchased a majority stake in the New Republic magazine and will become the venerable journal’s editor in chief and publisher.

Hughes introduced himself as the new owner of the Washington-based magazine, a leading exponent of liberal thought since its founding in 1914, with a self-written column Friday.

“In the next era of The New Republic, we will aggressively adapt to the newest information technologies without sacrificing our commitment to serious journalism,” wrote Hughes, 28. “We will look to tell the most important stories in politics and the arts and provide the type of rigorous analysis that The New Republic has been known for.”

The magazine offered no detail on the terms of the purchase. The news of Hughes’s new role is disclosed only at the bottom of Hughes’s column, in which he is identified as “publisher & editor in chief, the New Republic.”

A 2006 graduate of Harvard University, Hughes was among the group of college classmates who started Facebook with Mark Zuckerberg, Hughes’s roommate, in 2003. Forbes has estimated Hughes’s net worth at $700 million, but that was before Facebook filed this year to offer its first shares to the public.

Chris Hughes, co-founder of Facebook, listens to a question at the Charles Schwab IMPACT 2010 conference in Boston in October 2010. (ADAM HUNGER/REUTERS)

Hughes left Facebook in 2007 to serve as social-media director for Obama’s campaign, organizing an effort that raised record amounts of money.

For much of its existence, the New Republic has measured its success in terms of its influence among presidents and policymakers rather than circulation or profits. Over the years, it has published many of the leading intellectuals of the age, including George Orwell and political journalist Walter Lippmann, a founder.

Hughes will have a big challenge in turning around a biweekly publication that has had three owners in the past five years and has been losing readers for more than a decade. The magazine reportedly has a circulation of 50,000.

Hughes is purchasing the magazine from a group that includes Martin Peretz, its editor in chief from 1975 to 2010, and media financier Laurence Grafstein, the chairman of its advisory board.

In an interview with the New York Times on Friday morning, Hughes said he will continue to live in the New York area but will visit the magazine’s Washington office frequently. He will also continue to be involved with another venture that he founded, Jumo, an online outlet for charities.

“Profit per se is not my motive,” Hughes told the newspaper. “The reason I’m getting involved here is that I believe in the type of vigorous contextual journalism that we — we in general as a society — need.” He said he was investing in the magazine “because of my belief in its mission, not to make it the next Facebook.”

In a message to readers that accompanied Hughes’s column, Grafstein wrote, “With Chris’s leadership TNR will pursue its long-standing, ongoing mission of helping to define liberalism while contributing to the American project.”

The magazine said Richard Just will remain as editor. Peretz will serve on the magazine’s advisory board, although his precise involvement with the magazine is unclear.