President Trump said he would “always be friends” with China’s leader, but the two countries have been acting anything but these past few days. First, the U.S. slapped China with $50 billion in tariffs. Then, China retaliated with $50 billion in tariffs on U.S. goods, like soybeans and airplanes. Now, the U.S. has replied with $100 billion more. Vox’s Matthew Yglesias explains why this could escalate to a trade war, and really hurt Trump’s base.