PHILADELPHIA — A campaign consultant who helped federal prosecutors pursue a Pennsylvania Democratic congressman has been sentenced to four years of probation for his role in an illegal loan scheme.

Washington consultant Thomas Lindenfeld was a key government witness at this year’s trial of former Rep. Chaka Fattah (SHAW’-kah fa-TAH’) of Philadelphia.

Fattah was convicted of all 22 counts in the racketeering case. Sentencing is scheduled for Oct. 4. Six associates were also convicted, and the congressman’s son is serving a five-year term in a related case.

Lindenfeld told jurors that he helped Fattah obtain an illegal $1 million loan for his unsuccessful 2007 campaign for Philadelphia mayor.

The defense says Friday that Lindenfeld suffered from undiagnosed mental health problems at the time.

Fattah resigned days after his June conviction.