A senior Trump administration student-loan official appointed by Education Secretary Betsy DeVos resigned Thursday and said he would endorse outstanding student debt cancellation, calling the system "fundamentally broken," the Wall Street Journal reports.

The state of play: A. Wayne Johnson, who was the chief operating officer of the Office of Federal Student Aid before becoming the agency's chief strategy and transformation officer, said it's probable that much of the debt will never be repaid, citing repayment trends.

"We run through the process of putting this debt burden on somebody ... but it rides on their credit files — it rides on their back — for decades. The time has come for us to end and stop the insanity."

— A. Wayne Johnson told the WSJ

The big picture: The idea of wiping the $1.5 trillion student loan deficit clean is in the national spotlight after several Democratic candidates, including Elizabeth Warren and Bernie Sanders, incorporated it as a key campaign promise.

Roughly one-fifth of all student debt — federal and private, excluding students currently enrolled — is at least 90 days delinquent, according to the New York Federal Reserve, reports WSJ.

What's next: Johnson is planning a long-shot run for Republican Sen. Johnny Isakson's soon-to-be-vacated Georgia seat.

Go deeper... Special report: Higher education's existential crisis