In launching its case to the American public, the House committee investigating the Jan. 6 insurrection made a central argument: Look at the tape. The centerpiece of Thursday night’s hearing was a video reconstruction of the attack on the Capitol. Over 10 minutes, it went point by point, showing the rioters overwhelming and beating police officers as the mob broke into the building to stop the certification of Donald Trump’s election loss. The video had a powerful impact inside the hearing room and among Democrats.