BOSTON  “I’m not here to set any great records, or to make a spectacle,” Senator Bernard Sanders, independent of Vermont, said Friday, about a minute into his speech on the Senate floor. By the time he stopped talking, nearly nine hours later, Mr. Sanders was an ascendant, if unlikely, Internet star.

Mr. Sanders’s monologue, a marathon riff against the Obama administration’s plan to continue the tax policies of George W. Bush, stirred Twitter users to a roar over the course of eight-plus hours, putting his name atop the social network’s “trending topics” by Friday night. It garnered even more attention than when he was elected to the Senate in 2006 and was considered the first senator ever to identify himself as a socialist.

“I was a little bit nervous having never done this before,” Mr. Sanders, 69, said Saturday in a telephone interview from Burlington, Vt. “I was afraid that after two or three hours I’d have nothing more to say or I’d be tired or have to go to the bathroom. But I was pleased. It was very strange walking on there when the longest speech you’ve ever given in your life is an hour and a half.”

His legs were cramping during the speech, he said, so he jumped up and down for relief. His voice grew raspier by the hour. Toward the end, he was clutching the lectern with both hands, and it looked as if he might fall if he let go. His son Levi Sanders, watching from Boston and certain his father was hungry, considered having pizza delivered to the Senate floor.