A federal judge has sentenced Dennis Hastert to 15 months in prison in a hush-money case that centered on accusations that the former U.S. House speaker sexually abused at least four students when he was a high school wrestling coach.

Judge Thomas M. Durkin announced the sentence Wednesday. Hastert also must undergo sex offender treatment, two years of supervised release after his time behind bars and a $250,000 fine to go to a crime victims fund.

He pleaded guilty last fall to violating banking law as he sought to pay someone referred to as Individual A $3.5 million to keep sex abuse secret.

Before he sentenced Hastert, Durkin described the 74-year-old Illinois Republican as a "serial child molester," and that "accusing Individual A of extorting you was unconscionable."

Hastert was the nation's longest-serving GOP speaker and was second in the line of succession to the presidency.

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A former high school athlete who said he was sexually abused by Hastert when the former House speaker was his wrestling coach told a courtroom Wednesday that he was "devastated" after Hastert molested him.

The man's remarks were part of a victim-impact statement at Hastert's sentencing Wednesday at a federal courthouse in Chicago.

The man, now in his 50s, said Hastert abused him while they were alone in a locker room. He struggled to hold back tears as he described the incident in detail. In the years since, he said, he has sought professional help and has had trouble sleeping. He said the memory still causes him suffering.

He said he trusted and looked up to Hastert.

Moments before the man took the stand, a woman who says her brother was sexually abused by Hastert told the courtroom that he felt "betrayed, ashamed and embarrassed."

Jolene Burdge said Hastert abused her brother, Stephen Reinboldt, throughout his years at Yorkville High School, where Hastert was a history teacher and coach from 1965 to 1981.

Reinboldt died of AIDS in 1995.

His sister turned toward Hastert and said, "Don't be a coward ... tell the truth."

She also said, "I hope I have been your worst nightmare."

The statements were sure to turn up the pressure on Judge Thomas M. Durkin to reject defense calls for probation and send the Illinois Republican to prison.

If that happens, Hastert, who was second in the line of succession to the presidency after the vice president and the nation's longest-serving GOP speaker, would become one of the highest-ranking politicians in American history ever to be incarcerated.

Hastert pleaded guilty in October to violating banking reporting laws as he sought to pay someone $3.5 million. Prosecutors say it was hush money to conceal past sexual abuse against a student wrestler while Hastert was a high school teacher and coach. They say he abused at least four students throughout his years at Yorkville High School, about 45 miles southwest of Chicago.

The 74-year-old, who was pushed into the courthouse in Chicago in a wheelchair, agreed to a plea deal that suggested anything from probation to a maximum of six months behind bars.

But after prosecutors lifted a veil of secrecy from the case, the judge made comments suggesting he might impose a longer sentence, potentially putting Hastert behind bars for years, because of the abuse allegations.

Defense attorneys are seeking probation on the grounds that Hastert has already paid a high price in disgrace. They also cite his health, saying a blood infection nearly killed him in November and that a stroke has limited his mobility.

The lead prosecutor said he wishes Hastert could have been charged with the sexual abuse he was trying to cover up.

Assistant U.S. Attorney Steven Block called Hastert's conduct "horrendous." But because of the statute of limitations, Hastert could only be charged with a financial crime related to the payments he was making to one of at least four victims of sexual abuse.

Block said the sentence should take into account that Hastert "continues to deny what should now be obvious to everyone," that the payments were to conceal sexual abuse.

Defense attorney Thomas Green said he "acknowledges and respects" the pain of the man who described being molested as a teenager. He urged the judge to take into consideration the "entire arc" of Hastert's life, asserting that he reshaped his life as a public servant during his political career.

If the judge chooses, he could give Hastert the maximum sentence available -- five years in prison.

Until recently, it was hard to gauge what Durkin might be thinking. But at a recent hearing, he let his dismay show for the first time.

He singled out how Hastert in a 2015 interview with federal agents sought to deflect blame by falsely accusing Individual A of extorting him with a bogus sex-abuse claim. That lie would factor into the sentencing calculations, Durkin added: "That's a big one."

Earlier this month, prosecutors went into graphic detail about the sex-abuse allegations for the first time, even describing how Hastert would sit in a recliner chair in the locker room with a direct view of the showers.

Individual D, the one who plans to testify Wednesday, said he was 17 when Hastert abused him after offering the teen a massage, according to court documents filed by the government.

The victims, prosecutors said, were boys between 14 and 17. Hastert was in his 20s and 30s. The abuse occurred in a motel and the locker room at Yorkville High School outside Chicago.

It was not clear whether Hastert would make a statement at the sentencing and, if so, if it would include an apology.

Hastert has not personally apologized-- though his attorneys have described him as apologetic, saying their client "is deeply sorry ... his misconduct that occurred decades ago." Conspicuously absent was any mention of sexual abuse.

His lawyers may have risked raising the judge's ire when they questioned whether what Hastert did to Individual A -- including touching his genitals during a massage -- legally constituted sexual abuse.

Prosecutors hit back in their sentencing memo: "There is no ambiguity; defendant sexually abused Individual A."