William Barr first served as attorney general four presidents ago under George H.W. Bush. There was no reason to believe he had any particular affinity for Donald Trump before accepting the Cabinet post again.
Barr, 68, seems to be every bit as ideological and focused as Trump is transactional and impulsive.
While throwing blocks for the President, Barr is serving the national agenda of the political right and the principle of unitary executive power as advocated by former Vice President Dick Cheney.
In his widely-publicized speech to the Federalist Society last month, Barr condemned "the left" for "the systematic shredding of norms and the undermining of the rule of law."
"Unfortunately, over the past several decades, we have seen the steady encroachment on Executive authority by the other branches of government," he said. "This process, I think, has substantially weakened the function of the presidency to the detriment of the nation."
That's Barr's edge. He's a deeply-partisan backer of centralized authority.
Like Trump, Barr laments that conservatives are under siege. But when it comes to the details of Trump's theories regarding double-agent moles and stolen computer servers, Barr seems bent on treading carefully, maybe humoring his boss more than echoing him.
Barr let it be known this week that he disagrees with the Justice Department's inspector general on a key finding in an upcoming report — that the FBI had enough information in mid-2016 to start investigating members of the Trump campaign.
No "Spygate," no cabal and no "deep state" is expected to be laid bare in the long-awaited report by IG Michael Horowitz. Trump loyalists had hoped Horowitz would help delegitimize the scandal that resulted from the Trump campaign's Russia contacts.
Both Trump and Barr would like to call back the ugly and extensive details of special counsel Robert Mueller's probe on a kind of offsides penalty. If that earlier probe can be rendered illegitimate, so might be Democrats' efforts to charge Trump with obstructing justice when he tried to derail and remove Mueller.
So far, however, Trump shows no agitation as he did with Barr's predecessor Jeff Sessions. After the Horowitz report is released, Barr still is expected to keep Trump's denial hopes alive. The AG controls a separate upcoming report from Connecticut U.S. Attorney General John Durham.
“I do think the big report to wait for is going to be the Durham report. That's the one that people are really waiting for,” Trump said Tuesday, without specifying which people.
“And he's highly respected, and he's worked very hard, and he's worked long hours, I can tell you, and gone all over the world, so we'll see."
One thing we will see is the extent to which Barr is keeping Trump mollified. He did serve the greater purpose by telling Congress he thought Trump's campaign might have been spied on.
Barr has experience in this sort of muck. He pushed for the 1992 pardons that Bush granted for six people caught up in the Iran-Contra scandals.
If Barr's role is to protect Trump, that does not extend to shielding Trump's personal lawyer, Rudy Giuliani.
Two Giuliani associates involved in the Ukraine mess are under indictment in the Southern District of New York, part of Barr's Justice Department. Giuliani is under investigation there too.
Barr seems unlikely to worry much about that.
Recently Barr hailed Trump's presentation of the medal of freedom to President Ronald Reagan's onetime attorney general, Ed Meese.
At the White House, Meese, 88, praised Barr in particular.
Republican Giuliani, on the other hand, had quite a different history with Meese.
While Manhattan U.S. attorney under Reagan, Giuliani got an assistant to call Meese a "sleaze" in open court for interceding with the Pentagon on behalf of the corrupt Bronx-based Wedtech corporation.
As he left office in 1988, Meese blasted Giuliani, saying: ″I think it was poor procedure and poor practice by any prosecutor.″
For what's it's worth, Barr is unlikely to have forgotten about it.