Many politicians use Twitter and other social media simply to post campaign ads or other information they want to broadcast, Hemingway says. But one of his clients is a high-ranking Republican in Congress who will personally respond to tweets within five minutes.

Those who are using it “as a conversation tool, those are the guys getting the most out of it,” Hemingway says. “It’s a real-time 24-hour, seven-days-a-week town hall.... That’s the beauty of it.”

About 13 percent of American adults use Twitter, according to the Pew Internet & American Life Project, up from 8 percent in November 2010. Mr. Gingrich alone has more than 1.3 million followers on Twitter. Ms. Bachmann has just over 62,000.

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