I cannot pretend to know what drives Donald J. Trump to do most of the things he does, even though the public record as we approach the 18-month mark of his presidency does present some interesting questions.

Why does this man appear to be so intent on obliterating his immediate predecessor’s record?

President Barack Obama left two huge policy imprints on the nation before he left after serving two successful terms in office: the Affordable Care Act and the Iranian nuclear arms deal.

Donald Trump has sought to dismantle them both. The ACA remains on the books, more or less, after Congress grappled with ways to “repeal and replace” it with something we’ll call Trumpcare. The ACA became the prime target of the new president almost from the day he took office.

Now we have this withdrawal from the Iran nuclear deal. Secretary of State John Kerry worked day and night under Obama’s guidance to persuade our key allies to sign on to a plan that seeks to prohibit the Islamic Republic of Iran from obtaining a nuclear weapon.

Trump calls the Iran deal the worst in history. Has he read it? Does he really know what it says or what it requires? Well, that remains a wide-open question.

Trump’s obsessions with Barack Obama’s legacy has this hideous connection to another fixation he continues to have as it regards the 44th president: his place of birth.

It has struck more than one observer that Trump’s fomenting of the fiction that Obama was born in Africa and not in the United States is a racially tinged vendetta. What’s more, he has been a leader in the effort to discredit Obama’s eligibility because his father — who the president barely knew — was a Muslim. Trump has continued to allow that canard to become a talking point among some Americans who harbor sinister thoughts about Barack Obama’s ethnicity.

Trump’s behavior and his public statements throughout his presidency betray a dark side of the man. The Charlottesville, Va., riot and the moral equivalence he drew between racist rioters and those who opposed them speaks volumes to many of us.

The “birther” lie that Trump simply won’t disavow does as well.

Thus, I believe it is reasonable to presume that Donald Trump’s concerted effort to dismantle so much of Barack Obama’s legacy is born flatly out of racism.

Sickening.