Lawrence: Trump admin.’s childish threat of ‘economic D-Day’ is mocked by Iran as ‘improv night’

Tonight on The Last Word: Donald Trump’s Iran war nears six months as his hold on the GOP is tested in key races. Also, Democrats campaign on Trump’s unpopular war and economy. Plus, Democrats renew a lawsuit challenging Trump’s mail-in voting order. And Canada retaliates with up to 50% tariffs on U.S. products. Ali Velshi, Ben Rhodes, Iowa State Rep. Josh Turek, Andrew Weissmann, and Rep. Brendan Boyle join Lawrence O’Donnell.