CNN is using social media to build interactivity into the Republican presidential candidates debate Monday night, an approach it hopes to expand over the next 18 months of campaign coverage.

The network will allow people to pose questions online and discuss the responses, and it will add that conversation to the TV broadcast and the online video stream. People can use the Twitter hashtag #CNNdebate, John King’s Facebook page or tools on to participate.

The approach recognizes that the Internet has changed the once-passive audience into news participants. Since the 2008 election, Facebook has quadrupled in size (600 million active users now compared to 150 million then) and Twitter has become a mainstream medium. The Internet is changing millions of individual voters into millions of nodes in an electoral network, capable of sharing information and opinions with themselves and the candidates.

“Covering the campaign of 2012 and politics in general is not a one-way activity, it’s a two-way interactive process,” Bryan Monroe, editor of CNNPolitics, told me. “It is certainly taking our involvement with social media to a brand-new level. This is going to be a whole new ballgame.”

There are notable precursors to CNN's approach, such as the CNN/YouTube Debates of 2007. While they were impressive for their citizen involvement, the few dozen questions for each debate were screened in advance; it wasn’t truly interactive. (PBS Newshour and The Des Moines Register will hold another YouTube debate this January.)

Current TV’s “Hack the Debate” project combined a live-stream of the 2008 debates with curated tweets. Although that added an interesting social layer, those tweets still weren’t part of the debate itself.

Monday night’s debate will take the next step. Questions can be submitted in advance, but they’ll also be taken during the event. People can ask questions based on the answers they’ve heard so far, which should create something closer to a conversation between candidates and the users.

For example, Monroe said, if Mitt Romney dodges a question about the health care plan he enacted as Massachusetts governor, the person who posed that question can send a critical followup message that may be used by the moderator.

CNN will use software to filter the thousands of tweets and comments on Facebook and its website, but mostly it will be up to human curators to pick ones that add to the discussion.

The questions posed to the candidates are only part of the debate’s interactivity. Other questions and comments will be shown on CNN’s site next to a live video stream, and they’ll also form a “river” of messages flowing across the TV screen during the debate, Monroe said, similar to the Current TV approach in 2008.

Other extra elements will include a QR code on the TV screen that will take users to online content, including a column by Wolf Blitzer, a poll and a behind-the-scenes photo gallery. And a group of New Hampshire voters will be given handheld dials to register their reactions during the debate, with the results shown onscreen. That has been done in previous debates and State of the Union speeches.

CNN is hosting other debates in the coming months: in Tampa, Fla., the week of Labor Day, in Las Vegas on Oct. 18 and in Charleston, S.C., on Jan. 19. Other news outlets will organize debates as well. It should be interesting to see how CNN and others continue to transform the traditional debate program into an interactive experience.