Fmr. Sen. Majority Leader.: 'We're In A Dangerous Moment In Our History' | The Last Word | MSNBC

Lawrence O'Donnell talks to former Senate Majority Leader George Mitchell about President Donald Trump's comment that he wanted to increase the U.S. nuclear arsenal, the future of the Iran deal, and the power of the Senate to restrain Trump. » Subscribe to MSNBC: http://on.msnbc.com/SubscribeTomsnbc About: MSNBC is the premier destination for in-depth analysis of daily headlines, insightful political commentary and informed perspectives. Reaching more than 95 million households worldwide, MSNBC offers a full schedule of live news coverage, political opinions and award-winning documentary programming -- 24 hours a day, 7 days a week. Connect with MSNBC Online Visit msnbc.com: http://on.msnbc.com/Readmsnbc Find MSNBC on Facebook: http://on.msnbc.com/Likemsnbc Follow MSNBC on Twitter: http://on.msnbc.com/Followmsnbc Follow MSNBC on Google+: http://on.msnbc.com/Plusmsnbc Follow MSNBC on Instagram: http://on.msnbc.com/Instamsnbc Follow MSNBC on Tumblr: http://on.msnbc.com/LeanWithmsnbc Fmr. Sen. Majority Leader.: 'We're In A Dangerous Moment In Our History' | The Last Word | MSNBC