Brands love when social media stars take to Instagram or TikTok to advertise their soap, probiotic sodas, makeup and more. But many of those same brands are eager to avoid influencers who discuss politics. Making sure the two don’t mix has become a fraught exercise in the growing, and often unpredictable, influencer industry. With the presidential election looming, some marketing agencies have started to pitch advertisers on new tools that grade the so-called brand safety of social media personalities.