Former congressman Jesse Jackson Jr has pleaded guilty to misuse of about $750,000 (£490,000) in campaign money.
Jackson, son of civil rights leader the Rev Jesse Jackson, wept as he entered the plea at court in Washington DC. He faces up to five years in prison.
Prosecutors say Jackson used campaign funds for personal expenses and failed to report gifts.
The 47-year-old Democrat resigned in November after acknowledging he was being treated for bipolar disorder.
"Guilty, your honour," the former Illinois representative said after the federal judge asked for his plea to the conspiracy charge. "I misled the American people."
Jackson's father and other family members sat in the front row of the courtroom during Wednesday's hearing.
Jackson's wife, Sandra, also pleaded guilty on Wednesday, to tax fraud.
According to court documents, she admitted to failing to report $600,000 in income between 2005 and 2011. She faces one to two years in prison and a fine.
Prosecutors say that between 2007-09, the Jacksons used funds donated to his re-election campaign to buy a gold-plated Rolex watch worth more than $43,000, fur capes and parkas worth over $5,000, and nearly $9,600 on children's furniture.
He is also accused of failing to report $28,500 in gifts and loans to the House of Representatives, where he had served from 1995.
Officials may try to seize more than $60,000 in memorabilia and furs linked to the fraud.
Mr Jackson has also been under investigation by the House ethics committee over his dealings with imprisoned ex-Illinois Governor Rod Blagojevich.
Blagojevich was convicted of trying to sell an appointment to President Barack Obama's former US Senate seat and other corruption charges.