What secret from Denny Hastert’s past was so potentially damaging that federal prosecutors say the former U.S. Speaker of the House agreed to pay an individual $3.5 million to keep it concealed?

At this point, all we have are a few clues left by prosecutors pointing to unspecified “prior misconduct” by Hastert, possibly dating all the way back to his tenure as teacher and coach at Yorkville High School from 1965 to 1981, which was conspicuously mentioned in the first sentence of his indictment.

During that period, Hastert was the school’s celebrated wrestling coach.

The individual who was paid $1.7 million in installments by Hastert after confronting him in 2010 is described only as someone who has been a Yorkville resident and has known Hastert most of the individual’s life. The indictment says the misconduct occurred “years earlier.”

I think we can all make reasonable guesses about what that misconduct probably involves, although I don’t see any point in me speculating about it more specifically in print at this point.

As so often is the case, it wasn’t that original misconduct that tripped up Hastert anyway. It was the alleged cover-up.

Hastert’s mistake, as laid out in his indictment, was to make a series of large cash withdrawals in amounts just under $10,000 to avoid triggering a federal report that banks must file with the Financial Crimes Enforcement Network. This behavior drew the attention of the FBI and IRS because it can constitute a crime that the feds call “structuring.”

Then Hastert allegedly compounded his predicament by lying to the FBI agents who questioned him about it.