Alabama's Jeff Sessions was the first senator to endorse Donald Trump. For a long while, he was the only one. He has served as an adviser to Trump on a variety of issues, giving the campaign the perspective of someone who has been around politics a long time.

In an interview in Sessions' office Wednesday, I asked what he thought of reports that former President George H.W. Bush plans to vote for Hillary Clinton. Also, what about the other President Bush, George W., who has refused to endorse Trump? And Jeb Bush's public intention to vote for someone other than the GOP nominee? What was Sessions' reaction?

"Well, I don't know exactly where they are," Sessions began, "but millions of Americans, including this one, worked their hearts out for the Bushes in 1988, 1992, 2000, and 2004. And it wasn't Bill Clinton that helped the Bushes get elected. It was the same voters, in large part, that elected Ronald Reagan and stand to elect Donald Trump."

"I don't appreciate — " Sessions continued, pausing briefly when, it appeared to me, he thought better of what he was about to say. "I think they're not thinking clearly enough about this. They're not … appreciating half the American people, virtually, that have been supportive of Republicans. A lot of them preferred somebody other than Bush candidates, but they rallied around them when it came to November. So I would hope that we see more rallying."

I said that doesn't appear to be the case.

"Well, you never know," Sessions answered. "That's just a Democrat reporting what Mr. Bush said. I haven't heard him say anything."

The Democrat Sessions referred to is, of course, Kathleen Kennedy Townsend, who on Monday posted on social media a picture of herself and the elder Bush — they were together at a Points of Light Foundation meeting — with the note, "The President told me he's voting for Hillary!"

The disclosure set off warnings from Republicans to consider the source. After, a big Democrat like Kennedy would love to make a claim like that. But as the controversy grew, reporting indicated that Bush l did indeed say that to Kennedy. CNN's Jamie Gangel reported that Bush family members were livid with Kennedy over violating the privacy of the conversation — but they didn't deny that the senior Bush said what Kennedy said he did.

Other members of the Bush circle lamented the elderly former president's indiscretion in telling Kennedy. But again — no denial.

But even if Kennedy had never said anything, the stance of the Bush family in this election is remarkable. The only two living Republican former presidents, both Bushes, have refused to endorse, or to make any expression of support, or any statement of anything, about their party's current nominee. And Jeb Bush, the son and brother of presidents and a former candidate himself, refuses to endorse or make any expression of support for the man who defeated him for the GOP nomination. Even if the world did not now know that Bush I plans to vote for Hillary Clinton, that is an astonishing situation.

"I think they should remember the loyalty they were given by millions of Americans," Sessions said of the Bushes. "They should objectively analyze who is likely to advance best the agenda they favor and the agenda the Republicans who supported them favored. And that's clearly Donald Trump."

That was perhaps particularly directed toward the Bush who lost in the 2016 primaries. "Jeb signed the pledge," Sessions told me, referring to the promise Bush signed to support the eventual Republican nominee. "He needs to honor the pledge. All the candidates need to honor their pledge."

"And they try to pretend he's not a conservative," Sessions continued, speaking not just of Jeb but of Ted Cruz and John Kasich, who have also refused to back Trump. "That's ridiculous. At this point in history, it's the William F. Buckley test — who is the most conservative candidate that can win the presidency? Hillary Clinton or Donald Trump? On taxes, on regulations, on judges, on law enforcement — all these are conservative positions. What is the problem here? I just feel on issue after issue he's been firmly in the conservative, classical Republican conservative view."

There is one Bush supporting Trump. That would be George P. Bush, the current Texas Land Commissioner who is widely thought to be planning to seek higher office. In other words, the Bush family so dislikes Trump that the only Bush publicly supporting him is the one who hopes to face the voters again. George H.W. Bush, age 92, George W. Bush, age 70, and Jeb Bush, age 63, all have the luxury of not worrying about voter disapproval. George P., age 40, doesn't. So he backs Trump.

Sessions believes Trump will win more endorsements in coming days, and that Republicans will continue to come to support the party's nominee. That has certainly been the trend in recent weeks. The most recent Fox News poll of a two-way matchup between Trump and Hillary Clinton showed that Clinton had the support of 89 percent of Democratic respondents, while Trump had the support of 87 percent of Republicans. That's pretty close.

That's a big improvement for Trump, whose support among Republicans was in the 70s in some polls a few months ago. The fact is, as the race intensifies, many Republicans' partisan instincts are kicking in. They hear about Clinton aides smashing cell phones with hammers, about BleachBit, about Clinton's latest soak-the-rich, bust-the-budget proposals, and their response is to be a Republican who supporters the Republican nominee.

It also seems likely, although by no means certain, that Republican support of Trump will grow a bit more after voters see the two candidates side-by-side on the debate stage Monday. With third-party candidates nowhere to be seen, the race will become even more of a him versus her, Republican versus Democrat contest. That will likely help Trump with his own party's voters.

But not all of them, in particular not the only two Republicans who have served as President of the United States in the last 28 years. The Bushes appear determined not to come around, no matter what Jeff Sessions or anyone else wants.