A fight seems to have nearly broken out a congressional hearing. The Tuesday hearing in the Senate devolved into an angry confrontation between Sen. Markwayne Mullin of Oklahoma and International Brotherhood of Teamsters President Sean O’Brien. Mullin challenged the Teamsters leader to “stand your butt up” and settle longstanding differences right there in the room. Committee chairman Sen. Bernie Sanders of Vermont had to yell at Mullin to sit down after he challenged O’Brien to a fight. Mullin and O'Brien never came face to face in the room. But they hurled insults at each other for around six minutes.