She threw out a claim, got challenged, and immediately admitted, "I don't know." MSNBC’s Katy Tur got burned by making an unfounded claim during her show on Monday. She made a claim that has often been made as evidence of Trump-Russia collusion. “At the Republican National Convention, the Republican Party decided not to arm Ukraine against Russia,” Tur said, trying to wrap up her show. Former Trump campaign adviser Sam Nunberg interrupted her, however, and pointed out, “But Ukraine is armed.” The former adviser, who says he can no longer stand Trump, was most likely referencing reports that the Trump...