Stocks tumbled in morning trading on Wall Street Tuesday as a trade war between the U.S. and its key trading partners escalated, wiping out all the gains for the S&P 500 since Election Day. The tariffs between the U.S., China, Canada, and Mexico has helped to extend a recent slump for U.S. stocks that was prompted by signs of weakness in the economy. Subscribe to CTV News to watch more videos: https://www.youtube.com/ctvnews Connect with CTV News: For live updates and latest headlines visit: