The researchers’ data points to an evolving model of news media. While most news flowed from the traditional media to the blogs, the study found that 3.5 percent of story lines originated in the blogs and later made their way to traditional media. For example, when Mr. Obama said that the question of when life begins after conception was “above my pay grade,” the remark was first reported extensively in blogs.

And though the blogosphere as a whole lags behind, a relative handful of blog sites are the quickest to pick up on things that later gain wide attention on the Web, led by Hot Air and Talking Points Memo.