The trading platform Kalshi issued a three-year suspension to the candidate, Laurie Buckhout, and fined her nearly $2,600. Ms. Buckhout said she had made a “dumb mistake.”

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Republicans hold their trolls close. For Democrats, it’s more complicated.

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Scott Brown is chasing the political limelight again with a seemingly improvised Senate campaign.

© Aleksandra Michalska/Reuters