From Wikipedia:
During his first term, Symington was the subject of an investigation over his involvement with Southwest Savings and Loan, a failed Phoenix thrift. He was later cleared, and won reelection handily in 1994.
Later, he was indicted on charges of extortion and making false financial statements, and of bank fraud. He was convicted of bank fraud in 1997. The Arizona state constitution does not allow convicted felons to hold office, so Symington was forced to resign.