The White House is billing an event Wednesday as a real-time “conversation” with President Obama via Twitter.

But what will the discussion look like when participants are limited to 140 characters, the questions are filtered and the president isn’t typing?

The event may not be an easy task and may highlight the limits of Twitter, a popular and jumbled social-networking site being used by the administration to reach tech-savvy voters before the 2012 election.

Obama has held similar town halls this year on YouTube and at Facebook’s headquarters with chief executive Mark Zuckerberg. For those events, the president stayed close to script, repeating his desire to reduce the deficit and create jobs.

Perhaps the biggest outcome was the free publicity given to the format of those Web-based events. Obama’s discussion Wednesday will give a high-profile endorsement to Twitter, the latest Silicon Valley darling to develop ties with the administration.

Co-founder Jack Dorsey has advised the State Department on how Twitter can be used in repressive regimes. Chief executive Dick Costolo serves as an adviser to Obama on telecommunications policy and national security. Former State Department aide Katie Stanton joined Twitter as its vice president of global policy.

“We’re always on the lookout to have a productive interactive discussion with the public in new and exciting ways,” White House Communications Director Dan Pfeiffer said. “It’s similar to what [past] presidents did with [TV] networks and newspapers.”

On Wednesday, Dorsey will moderate the town hall from the White House. He will select questions from thousands submitted before the event and more from live messages known as tweets. He will run an algorithm that searches for tweets with the phrase “#AskObama” and choose the most common topics, according to Twitter. The company can block topics deemed inappropriate.

The president will dictate responses to his staff and Twitter officials, who will put out his answers within Twitter’s 140-character limit using the account @townhall or @whitehouse.

Expected hot topics are personal finance and national security, according to Radian6, the company that will run the search algorithm.

Not everyone believes Twitter is the best format for a town hall. Its system for searching and sending messages can be overwhelming for some users.

“It’s like drinking out of a fire hose,” said Alan Webber, an analyst at media consulting firm Altimeter Group. “These are hardly one-on-one conversations.”

But a Twitter spokesman said the event could be a breakthrough.

“This is a new type of conversation, one that for new users can be very approachable,” said Adam Sharp, Twitter’s Washington-based official in charge of political outreach.

Even with social networking’s quirks, politicians have been embracing the platform.

Obama has had a Twitter account since 2007 and sent his first personal tweet last month on Father’s Day. Vice President Biden opened his account last weekend, wishing military families a happy Fourth of July.

But social networking has also gotten some in trouble — Anthony Weiner’s political career collapsed after the New York congressman tweeted a lewd photo of himself.

About 13 percent of people online used Twitter last month compared with 8 percent last November, according to a study by the Pew Research Center’s Internet & American Life Project. Twitter users tend to be young professionals who are politically engaged, Pew said.

“More people are getting their political news from newspapers and television, but those on social-networking sites tend to be politically active. So politicians who are on Twitter are punching above their weight in terms of getting people to donate money and talk to friends about candidates,” said Aaron Smith, a researcher at Pew.