With clipboard in hand and "don't tread on me" rattlesnake earrings dangling, Jenny Beth Martin, the woman sometimes described as the tea party's den mother, stood guard over the microphone at a Capitol Hill protest of the Internal Revenue Service's targeting of conservative groups.

Lawmakers sweltered in a long line waiting to take the stage earlier this summer before a crowd of roughly 10,000 and a live Web audience. It was up to Mrs. Martin to decide who would get a turn.

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