TikTok, the booming social media app, became a football in the Republican debate Wednesday night. Stuart Varney, one of the moderators, asked Vivek Ramaswamy why he had joined the app while meeting with an influencer, noting that TikTok had been “banned on government-issued devices because of its ties to the Chinese government.” Mr. Ramaswamy defended his use of TikTok, saying he was trying to reach a younger generation, though he argued that children under 16 should not be on “addictive” social media. “I have a radical idea for the Republican Party: We need to win elections,” he said. “Part of…