WASHINGTON — The book jacket for J. Dennis Hastert’s 2004 memoir, “Speaker,” proudly notes how little known he was by the public despite being one of the most powerful people in America.

“Not because he has anything to hide,” it says, “but because he doesn’t care who gets the credit.”

It turns out that John Dennis Hastert did have something to hide, something quite reprehensible. Now his admission in federal court that he sexually molested wrestlers on the Illinois high school team he coached years before setting foot on Capitol Hill is provoking a re-evaluation of his tenure as the longest-serving Republican speaker. And Mr. Hastert fares poorly in this new light.

The bill of particulars is lengthy. Consider the Mark Foley page scandal. An explosion in questionable “earmarking” for pet legislative projects. The neutering of an already weak ethics process. Hardball tactics on the House floor. A weakening of committee chairmen accompanied by heightened pressure on them to leverage legislative clout to raise campaign money. Undue deference to the executive branch. Personal enrichment.

Take those together with the shocking revelations of sexual abuse of youths placed in the trust of Mr. Hastert, a popular and successful coach, and he emerges as a deeply flawed figure who contributed significantly to the dysfunction that defines Congress today. Even his namesake Hastert rule — the informal standard that no legislation should be brought to a vote without the support of a majority of the majority — has come to be seen as a structural barrier to compromise.