"Among Europeans, there's a high level of trust that he's made the right moves," observes Daniel Ziblatt, a Harvard professor who's a co-author of the book "How Democracies Die."

Among Americans, trust has proved exceptionally hard to find.

Polarization makes rigid Republican opposition a given. But a thoroughly sour public mood -- whether the result of Biden's actions or not -- has dispirited fellow Democrats and sent independents toward the GOP less than five months before Election Day.

"Our republic is on a river heading toward a cliff," says Ian Bassin, director of the advocacy organization Protect Democracy. "We're about to go over it."

"Our democracy today is on a knife's edge," said Luttig, once on President George W. Bush's short list for a Supreme Court appointment.

They've painted a clear and consistent portrait: of a President who relentlessly sought to erase the verdict of American voters even though he knew it was both groundless and illegal. The consequences were deadly.

Biden, like his party and the modest faction of pro-democracy Republicans, can only hope the hearings slow a return to power by the leaders who spawned and have tolerated that threat to the American system. There's little sign that previous attempts have had much effect.

Desperate for progress, Bassin wants Biden to consider new approaches, some of them highly unconventional for any president. A legislative deal with congressional Republicans restricting some instruments of executive authority, for example, could help "fireproof" the White House against a future would-be tyrant.

That Republicans have become "the Achilles' heel" of American democracy, as Ziblatt puts it, has historical precedent. The preservation of democratic systems, he says, has typically depended on whether center-right parties representing traditional powers within a society adapt to competing in elections rather than thwarting them.

This year, Republicans command such high political ground that they may not need to challenge election results. But Republican ascendance this fall, like Biden's 2020 victory, won't resolve the fight to preserve democratic institutions.

"It will make the mountain we need to climb that much higher," Bassin insists, "but we still need to climb it."