A 61-page report carrying the seal of the U.S. Treasury Department’s inspector general offers a tutorial for Republican senators interested in challenging Penny Pritzker’s commerce secretary nomination.

The document chronicles the 2001 failure of a suburban Chicago bank after Pritzker and her family expanded subprime lending there and did pioneering work with the kind of mortgage-backed securitization that would eventually spread and help spark the worst recession since the Great Depression.

In a May 2001 letter to the Superior bank’s management and employees -- just two months before its closure -- Pritzker detailed a plan to revive the institution with an expansion into subprime lending. She wrote that her family was devising a $351 million recapitalization plan for the bank.