Despite its name, the January 6 committee is not merely investigating the storming of the US Capitol in 2021. It is rightly examining the broader campaign to deny the will of the people. Its first public hearing on Thursday highlighted the terror of a day that led to the deaths of at least seven people and saw 140 police officers injured as a mob, armed with cable ties and stun guns, wielded flagpoles as clubs. Graphic footage and vivid testimony from a Capitol police officer – “I was slipping in people’s blood … It was carnage” – reminded primetime viewers just how shocking and frightening those events were.

Yet the greater horror is that the riot was not an anomaly, but the “culmination of an attempted coup”, part of a months-long effort to overturn the election result. It happened when more genteel methods had failed, though they got much further than they should have. “President Trump summoned the mob, assembled the mob and lit the flame of this attack,” said Liz Cheney, the House select committee’s vice-chair.

Rioters have already been jailed. But those most culpable have yet to be held accountable. The committee’s exhaustive efforts have established genuinely shocking revelations: when Donald Trump learned that supporters were chanting “Hang Mike Pence”, he reportedly remarked that his vice-president might “deserve” it. The sheer number of those in his inner circle – including his daughter Ivanka – who were clear that he had lost and, in many cases, told him so, was damning. Establishing that Mr Trump knew full well that Joe Biden had won might, potentially, help to build a legal case against him. That task, however difficult, looks simple compared to the challenge of changing voters’ minds, already largely made up. Many of the worst aspects took place in full view. Mr Trump repeatedly lied that the election had been stolen. He urged his supporters “to fight like hell”. He refused to call them off when begged by top Republicans. As one rioter said, “I answered the call of my president”.

Most Americans – 70% – believe that finding out what happened that day matters, but 52% of Republicans judge it not very or not at all important. In a world of “alternative facts”, the truth can simply be ignored: Fox News did not broadcast the hearing.

As November’s midterms approach, voters appear more concerned about the cost of living than threats to democracy which they may, wrongly, imagine to have been overcome. At best, the hearings may boost Democratic fundraising, persuade a few reluctant voters to the polls, or give pause to the undecided who were thinking of giving Republicans another chance. Mr Trump remains the favourite to be his party’s presidential candidate in 2024. Senior Republicans who denounced him after the riot fell quickly and shamefully silent; Ms Cheney and her colleague Adam Kinzinger have been vilified for serving on the committee.

The committee is not only establishing the historical record, but seeking to safeguard institutions in the future. Next time, Republicans will be more organised and more ruthless in pursuing victory whatever the ballots say.

The GOP has systematically sought control of election processes and installed its people in the judiciary. The far right – including members of militias who played a critical role in the January 6 attacks, such as the Proud Boys – are moving off the streets and seeking elected office. Next time, no mob may be required. Just as the storming of the Capitol was one in a series of assaults upon democracy, so this must be only one of many attempts to uphold it. If these hearings appear to preach to the converted, they are no less essential. The alternative – giving up – is unthinkable, because the Trumpists haven’t, and won’t.