Senior Regional Correspondent

Crusading federal prosecutor Ron Machen has taken a major step forward in his crackdown on District political corruption by fully exposing a long-standing illegal campaign donation network allegedly run by top city contractor and power broker Jeffrey E. Thompson.

The accomplishment seems likely to put Machen in a position to press Thompson to answer a key question with the potential to sink Mayor Vince Gray’s political future: What did Gray (D) know about the $650,000 “shadow campaign” that helped elect him in 2010?

Those are early highlights of what Machen has promised will be fast-moving investigations in the coming months, including of the mayor. We’ll learn more detail about the illegal donation network on Thursday with a planned guilty plea by one of Thompson’s former employees, Lee A. Calhoun.

“You are beginning to see significant developments, and I expect that we will continue to be busy as we work to get to the bottom of this,” Machen, whose title is U.S. attorney for the District of Columbia, said in an interview this week.

The accelerated pace improves the chances that District voters will know enough before the April Democratic primary to judge whether Gray is too damaged to seek reelection. It also ought to silence critics of Machen who whine that his probe is taking too long and unfairly casting a pall over the mayor.

D.C. corruption scandals: A look at the investigations and where they stand.

(If the mayor has done nothing wrong, as he says, then presumably he could dispel the cloud by clarifying how it happened that he benefited from massive illicit donations and that three people who worked with his campaign have pleaded guilty to crimes. But citing Machen’s investigation, he’s stayed silent.)

Now, we’ve known for a while that the shadow campaign existed and that Thompson was supposedly at the center of it. But that was based mostly on last year’s guilty plea by public-relations consultant Jeanne Clarke Harris.

What’s new are three developments in the past 10 days that provide corroboration that an illicit campaign funding network has existed for years, that Thompson oversaw it, and that he pressured his employees and others to participate.

First, there’s the scheduled guilty plea by Calhoun. His attorney, Edward B. MacMahon, indicated it would lay out how Thompson pushed employees to become “straw donors” by using their names to conceal his donations.

“There isn’t any doubt this was all the Jeffrey Thompson show,” MacMahon said. He said Calhoun would plead guilty to a misdemeanor campaign finance violation and predicted others would make similar pleas in the future.

“What you’re going to see in the next few months is people suffering the consequences of having gotten involved with, or been influenced by, Mr. Thompson to make these donations,” MacMahon said.

That account was reinforced by a revealing statement Friday by Thompson’s former accounting firm, Bazilio Cobb Associates. It said that Thompson had directed “employees, family members and their friends” to donate “significant amounts” of money to political campaigns over 10 years.

It added that Thompson “may have violated federal campaign law by giving directions to reimburse, with his own funds or with corporate funds, employees and others who made such contributions.” Thompson is not charged with a crime.

Finally, there was last week’s guilty plea by former D.C. Council member Michael A. Brown. Among other things, his plea agreement said Thompson provided hundreds of thousands of dollars of secret funds to benefit candidates.

All this suggests that the U.S. attorney is accumulating evidence and witnesses that could support possible charges against Thompson. A court document says he is the subject of a grand jury investigation. His attorney declined to comment.

Where does that leave the mayor? At this point, it’s all hypothetical. But Machen, like any prosecutor, works from the bottom up. He’s clearly using foot soldiers such as Harris and Calhoun to build as strong a case as possible against Thompson.

That could give the prosecutor leverage, one presumes, to force Thompson to say all he knows about Gray. So far, Thompson has fought the probe relentlessly. But he might turn cooperative if the alternative were the risk of many years in jail.

There’s always the possibility that Thompson could exonerate Gray or wouldn’t give Machen enough to indict the mayor. The prosecutor would want a virtually airtight case to bring such a high-profile prosecution.

At a minimum, though, Machen’s exposure of the illegal campaign funding operation has shut down a major source of political corruption in the District. He also could procure important insights before next year’s election about the mayor’s involvement or lack thereof.

I discuss local issues Friday at 8:50 a.m. on WAMU (88.5 FM). For previous columns, go to