Many eyes will be on Chris Wallace when the two major-party candidates for president square off later this week.

The Fox News anchor will moderate the upcoming debate between Democrat Hillary Rodham Clinton and Republican Donald J. Trump.

I have a long list of questions that Wallace ought to ask. I know he’s likely to ask Clinton about the e-mails being leaked and whether they undermine her ethical standards. I also believe he’ll ask Trump about that “Access Hollywood” recording about the GOP nominee’s conduct with women.

But here’s a potential set of questions I hope Wallace will ask. They should go to Trump:

“Mr. Trump, you once praised Hillary Clinton as a ‘great person.’ You have played golf with her husband, the former president. You have attended parties with them. You’ve been photographed arm-in-arm with both of them.

“What changed? How did the former president and the current Democratic nominee for that office go from being friends of yours to becoming mortal political enemies?”

There’s something potentially revealing to me about Trump’s change in attitude toward the Clintons, now that he’s launched this scorched-Earth campaign against Hillary while seeking to drag Bill into the discussion over his wife’s fitness to become president.

It’s fair to wonder if Trump is nothing more than an opportunistic back-stabber. It’s also fair to ask if he schmoozed with the Clintons for self-serving purposes only. It’s also fair to wonder if he still harbors warm-and-fuzzy feelings toward them and he’s saying all these venomous things about Hillary for purely political purposes.

Trump did, after all, declare that he said those nasty things about women for “entertainment.”