WASHINGTON—Twitter Inc. on Tuesday turned down a widower’s request to delete tweets by President Trump floating baseless theories about his wife’s death, but for the first time applied a fact-checking notice to a different unsubstantiated claim the president made on the platform.
The social-media company didn’t explain its decision early in the day not to remove Mr. Trump’s tweets falsely suggesting that former lawmaker and current MSNBC host Joe Scarborough had played a role in the 2001 death of a former congressional aide.
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