Despair is worse after hope is briefly ignited. I don’t know about you, but I was elated earlier this spring when it seemed as if Trump and Covid were gone, and Biden seemed surprisingly able and willing to get the nation rapidly back on track.

Now much is sliding backwards. It’s not Biden’s fault; it’s Trump’s legacy.

The new Delta strain of the virus requires, according to the CDC, that we go back to wearing masks inside in public places where the virus is surging, even if we’re fully inoculated.

This would be nothing more than a small disappointment and inconvenience were it not for Republicans using it as another opportunity to politicize public health.

House Minority Leader Kevin McCarthy responded to the new CDC recommendation with the kind of unhinged hyperbole Trumpers have perfected. “The threat of bringing masks back is not a decision based on science, but a decision conjured up by liberal government officials who want to continue to live in a perpetual pandemic state,” he said.

Republican politicizing of public health will get worse if the Delta variant continues to surge. At some point vaccines will have to be mandated because being inoculated is not solely a matter of personal choice. Herd immunity is a common good. If infections mount, that common good can be achieved only if nearly everyone is vaccinated.

But those eager to exploit the virus’s resurgence – the know-nothings, Trump wannabes, vilely ambitious political upcomers, Tucker Carlsons and similarly cynical entertainers – are already howling about “personal freedom” threatened by “socialism.”

The investigation into the attack on the US Capitol on 6 January is further evidence of how far the Republican party has descended into opportunistic treachery.

We need to know what happened and why if we are to have half a chance of avoiding a repeat. Just as with the history of systemic discrimination and brutality against Black people in America – which Republicans are calling “critical race theory” and trying to ban from classrooms – the truth shapes our responses to the future.

Here again, the dispiriting aspect of the present moment is Republican denial and obfuscation.

As Officer Michael Fanone – who suffered traumatic brain injury when rioters attacked him during the assault on the Capitol – testified yesterday at the start of the hearings: “What makes the struggle harder and more painful is to know so many of my fellow citizens – including so many of the people I put my life at risk to defend – are downplaying or outright denying what happened.”

With the exception of Representative Liz Cheney – whom I never expected to hold up as a model of integrity – Republicans are eager to divert the public’s attention. Republican Conference Chair Elise Stefanik declared at a press conference on Tuesday that “Nancy Pelosi bears responsibility, as speaker of the House, for the tragedy that occurred on January 6.”

This is absurd on its face. The Speaker of the House shares responsibility for Capitol security with the Senate majority leader, who at the time of the attack was Mitch McConnell. If Pelosi was negligent – and there’s zero evidence she was – McConnell was as well.

Stefanik and other Republican leaders don’t want the public to know about Republican members of Congress who were almost certainly involved in the travesty, either directly or indirectly. The list includes Representatives Jim Jordan, Mo Brooks, Paul Gosar, Matt Gaetz, Marjorie Taylor Greene, Lauren Boebert, Andrew Biggs and McCarthy himself. Senator Josh Hawley also seems to have been in the know, given his fist-salute to the rioters.

And then there’s Trump himself, cheerleader and ringleader.

All should be subpoenaed. All, presumably, will fight the subpoenas in court.

Meanwhile, Trump continues to stage rallies for his avid followers as he did last weekend in Phoenix, where he declared, “Our nation is up against the most sinister forces … This nation does not belong to them, this nation belongs to you.”

Wrong. America belongs to all of us. And we all have a responsibility to protect its public health and its democratic institutions. The real sinister force is the Trump Republicans’ cynical exploitation of lies and anti-scientific rubbish to divide and divert us.

Months ago, it seemed as if this darkness was behind us. It is not.

• Robert Reich, a former US secretary of labor, is professor of public policy at the University of California at Berkeley and the author of Saving Capitalism: For the Many, Not the Few and The Common Good. His new book, The System: Who Rigged It, How We Fix It, is out now. He is a columnist for Guardian US.