Correction: An earlier version of this article said that Jeffrey E. Thompson pleaded guilty Monday to funneling more than $42 milllion in illegal contributions to campaigns. The correct figure is $2 million. This article has been updated.

From the archives: An overview of Jeffrey Thompson's significance in D.C. politics and connections to key figures. There have been more guilty pleas in connection to the ‘shadow campaign’ since this video was originally published in July 2013. (The Washington Post)

Jeffrey E. Thompson’s guilty plea on Monday marks the culmination of a years-long federal investigation into District political corruption. It also marks a defining moment for the 58-year-old self-made businessman, an immigrant who built an accounting and health-care empire that has crumbled amid allegations of wrongdoing.

Jeffrey Earl Thompson was born in 1955 into a working-class home in Jamaica’s St. Elizabeth Parish, the youngest of 11 children. He came to Washington in 1975, earning a high-school equivalency degree and putting himself through the University of the District of Columbia by working as a bookkeeper.

Not long after graduating from college and interning at top accounting firms, in 1983 he founded his own company, which would become Thompson, Cobb, Bazilio & Associates. Over the next two decades, he would build it into a national powerhouse among minority-owned firms, in no small part because of its ability to win local and federal government contracts.

He became a frequent donor to political campaigns in the District, the Washington region and beyond, and cultivated close relationships with national figures, including civil rights icon Dorothy I. Height and former labor secretary Alexis Herman.

Thompson played a key role in the rise of Anthony A. Williams. Not long after Williams became D.C. mayor in 1999, Thompson moved to take advantage of changes in the city’s health-care system, buying out of bankruptcy a small insurance company, D.C. Chartered Health Plan. Over the next decade, Chartered became the city’s dominant Medicaid contractor. By 2012, it managed the health care of more than 100,000 low-income city residents and collected more than $300 million in government funds.

Thompson’s fortunes took a sudden turn on March 2, 2012, when federal agents raided his home and downtown offices, revealing that an investigation rooted in allegations of illicit cash payoffs by Vincent C. Gray’s mayoral campaign had expanded significantly.

The scope of the investigation became clear the following July, when a longtime associate of Thompson’s, public relations consultant Jeanne Clarke Harris, pleaded guilty to felony charges of funneling funds from businesses owned by a co-conspirator. Those funds went to family members and friends who then made donations to political candidates.

As a part of Harris’s plea, federal prosecutors outlined $653,000 in spending made in support of Gray’s campaign, spending that was not reported to government regulators as required by law.

In the 20 months since the Harris plea, Thompson has figured into the prosecutions of five additional figures — a close friend of Gray’s who admitted to playing a key role in the “shadow campaign”; two former employees of the accounting firm, who said Thompson directed them to make illegal “straw donations” for which they were reimbursed; and a former D.C. Council member who said Thompson secretly gave him $20,000 to finance a 2007 campaign.

The September plea of a New York-based political consultant alleged that Thompson had a hand in funding $600,000 of unreported campaign work on behalf of Hillary Rodham Clinton’s 2008 presidential campaign. As part of his plea, Thompson admitted has involvement in that effort.

As the prosecutions unfolded and Thompson found himself regularly in the headlines for the first time in his career, his business fortunes faltered. After the raids, he sold his $1.2 million Crestwood home and other real estate, sold his interest in the accounting firm and moved to sell his health-care firm.

In October 2012, city regulators placed Chartered Health Plan into receivership, citing financial irregularities. The company lost its lucrative city contract, and a judge last year approved the sale of its most valuable assets to a Philadelphia-based firm for $5 million. The receiver has sued Thompson, accusing him of diverting funds from the company’s accounts, and is seeking $17 million.

On Monday, Thompson pleaded guilty to funneling more than $2 million in illegal contributions to campaigns, including Gray’s 2010 mayoral bid. He could face at most six months in prison, followed by three years of supervised release.