William Pelham Barr has emerged — in my mind, at least — as Donald Trump’s latest “only grownup” in his administration.

Now that former Defense Secretary James Mattis has exited the Trump administration, it now falls on the attorney general-designate to assume the role of grownup.

Based on what I have heard during two days of testimony before the U.S. Senate Judiciary Committee, Barr might be ready to step into that key role.

Barr would take over a Justice Department that supervises the investigation of special counsel Robert Mueller, who is examining whether Donald Trump’s presidential campaign “colluded” with Russians who interfered in our 2016 election.

Barr has hit several pitches out of the park. He vows to let Mueller complete his probe without interference; he pledges that he would not follow an unlawful order from the president; he stands by Mueller — with whom he has been friends for 30 years — as man of impeccable integrity; he says Mueller is not engaged in a “witch hunt”; he says he won’t be “bullied” by the president of the United States.

OK, with all that said, Barr did whiff on at least one pitch from the Senate Judiciary Committee. He won’t mess with laws governing whether a president can be indicted. Nor did he promise to make the Mueller report public, which I believe is imperative, given the public expense of the investigation.

In the grand scheme, I believe Barr should be recommended for confirmation by the Judiciary panel and the full Senate should confirm him. He won’t get the unanimous confirmation he got when he served as AG during the George H.W. Bush administration from 1991 to 1993. It’s a different era now. A different type of president has taken office and he has upset almost every single element of what we used to call “normal” in American politics.

Trump fired Jeff Sessions as AG only because Sessions recused himself from the Russia matter. Sessions did what he had to do under DOJ rules of ethics. There could no way for him to lead an investigation into a presidential campaign in which he played a key role as a national security adviser. So he backed out, enraging Trump.

Barr promises he won’t be bullied by the president. I hope he stands firm on that. He no doubt knows what he is getting into by accepting this job as attorney general.

Which to my mind makes him a serious grownup in an administration that is sorely lacking in them.