That's a heavy lift, given Barr's distinguished service to Donald Trump's presidency via distortion of the conclusions of special counsel Robert Mueller's report and his politicisation of the Department of Justice.

But Barr's depiction of Trump as being "detached from reality" after the election does have independent significance. It demonstrates that it is possible to have been a loyal Trump supporter - nay, an enabler - through the investigation of the possible collusion with Russia and the Ukraine-related first impeachment, yet still draw the line at Trump's efforts to overturn the results of a presidential election.

This in turn matters for what it might mean for the future of Republican politics. Maybe, just maybe, Barr's position can help signal to Republicans that election denialism shouldn't be the future of the party - and that Trump can be left behind.

In this admittedly idealised scenario, it is not precisely that Republicans at all levels of government could be expected affirmatively to deny the existence of fraud in the 2020 elections. Rather, they would just gradually stop talking about it.

And because Trump himself clearly cannot and will not acknowledge his defeat, changing the subject would be a sign for Republicans, including his current supporters, to get over Trump himself. They could transfer their attention to would-be Trumps like Ron DeSantis and JD Vance.

Our long national nightmare of Donald Trump would not exactly be over. Trumpism could live on without him. It might conceivably become more dangerous. But at least the man himself, who posed a threat to the future of democracy unmatched in the history of the republic, would be eased from the scene.

Listening to Barr's testimony was a reminder of just how convincing the lawyer can be - and why he demonstrates a kind of evil genius for bureaucratic self-preservation. To hear Barr tell it, before the election he found it possible to deliver hard truths to Trump. There was sometimes "wrangling," but Barr said he felt able to get his message across.

The idea that Barr could, before the election, somehow speak truth to power to Trump sounds pretty far-fetched at best. Trump badly needed his attorney-general to help get through the Mueller investigation debacle. Barr joined the administration knowing full well that the president needed him. If Trump listened to Barr or appeared to, it was no doubt because Barr had leverage over his boss while his administration was at its most vulnerable juncture.

After the election defeat, Trump no longer needed the nearly unique legal and political skills that Barr deployed in saving the president from the consequences of his actions. He needed lawyers who would take affirmative steps to overturn the election. Once he understood that Barr wasn't going to do that, he was able to dismiss Barr's advice that the claims of election fraud were "bull----."

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The thing is, the plausibility of Barr's assertion about his relationship with Trump before the election is irrelevant to the deeper issue of whether Barr can help the Republican Party free itself of Trump now. Barr is no popular (or populist) politician, to be sure. He's a DC insider, the political appointee's political appointee.

Nevertheless, he demonstrated genuine loyalty to Trump in the past. He didn't even tell the world why he was resigning when he did. Without the events of January 6, he might never have come forward at all with his account of Trump's post-election behavior. That loyalty could be read to justify the truth of Barr's post-election conclusion that Trump had become unhinged by losing and could not rationally accept defeat.

Barr's testimony provides a useful, usable story Republicans might be able to accept, albeit quietly. Simply: Trump was a great president. There was no Russia collusion. The first impeachment was illegitimate. Then Trump lost the election. What followed was regrettable - and should now be repudiated or at least forgotten.

So far, the would-be post-Trump Trumpists are too worried about alienating his followers to do so. But that could change if politicians like DeSantis and Vance sense that there is room for them to say, Trump is dead, long live Trumpism. To the extent Barr's testimony contributes to that possibility, that's something everyone should welcome. The Democrats who not so secretly hope Trump runs for president again, gambling that he would be far less electable than another Republican, have to consider what's good for the country. Even if a clear majority of voters reject him, we have come too close to seeing how one man could pave the way for the eventual democratic failure in the United States.