Senator Markwayne Mullin challenged Teamsters President Sean O'Brien to a fight during a hearing of the Senate Committee on Health, Education, Labor and Pensions. Senator Bernie Sanders attempted to cool things down. » Subscribe to MSNBC: http://on.msnbc.com/SubscribeTomsnbc Follow MSNBC Show Blogs MaddowBlog: https://www.msnbc.com/maddowblog ReidOut Blog: https://www.msnbc.com/reidoutblog MSNBC delivers breaking news, in-depth analysis of politics headlines, as well as commentary and informed perspectives. Find video clips and segments from The Rachel Maddow Show, Morning Joe, The Beat with Ari Melber, Deadline: White House, The ReidOut, All In, Last Word, 11th Hour, and Alex Wagner who brings her breadth of reporting experience to MSNBC primetime. Watch “Alex Wagner Tonight” Tuesday through Friday at 9pm Eastern. Connect with MSNBC Online Visit msnbc.com: http://on.msnbc.com/Readmsnbc Subscribe to the MSNBC Daily Newsletter: MSNBC.com/NewslettersYouTube Find MSNBC on Facebook: http://on.msnbc.com/Likemsnbc Follow MSNBC on Twitter: http://on.msnbc.com/Followmsnbc Follow MSNBC on Instagram: http://on.msnbc.com/Instamsnbc 'Stand your butt up!' Near brawl at Senate hearing #Senate #MarwayneMullin #BernieSanders