The federal raid Friday on contractor Jeff Thompson’s home and office is providing fresh ammunition for three candidates hoping to unseat Council member Vincent B. Orange (D) in the April 3 Democratic primary, but Orange maintains he’s not worried the widening corruption probe will impact his race.

Within hours of the raid, former Prince George’s County Council member Peter Shapiro and former council member Sekou Biddle were both pointing to published reports that Orange has collected $100,000 in campaign donations from Thompson.

Little is known about why IRS and FBI agents raided Thompson’s office on Friday.  Thompson did not return messages left at his home and office Friday evening, but officials who spoke about the probe on condition of anonymity did not allege that Thompson broke any laws.

Vincent Orange listens to an opponent. (Sarah L. Voisin/The Washington Post)

Thompson, owner of Chartered Health Plan, the city’s largest contractor, has contributed or raised hundreds of thousands of dollars for District political officials, including Mayor Vincent C. Gray (D) and former Mayor Adrian M. Fenty (D).

Last year, the Washington City Paper calculated that Orange, who unsuccessfully ran for mayor in 2006 and council chairman in 2010, has collected at least $100,000 from Thompson and his companies over the past decade. In July, The Washington Post reported that half of the money Orange has raised in his 2011 council campaign came from people with ties to Thompson.

 Biddle referenced the donations in an e-mail solicitation he sent to supporters Monday morning.

“It's time to end this culture of corruption and pay to play on the DC council,” Biddle wrote. “We need ethical leaders who serve the residents of the District and not their own financial interests.”

Shapiro is also taking aim at Orange’s ties to Thompson.

“Council member Orange has a lot to answer for before he can ask the public to return him to office,” Shapiro said in a statement. “He has received over $100,000 in contributions tied to Mr. Thompson, who is now under Federal investigation after his offices were raided Friday. His campaign finance reports from this year and 2011 include countless instances of missing information and questionable money-order contributions. District voters deserve to know what’s going on.”

Orange, who has an edge in early polling of the race, noted Saturday there “has been no allegation of wrong doing” by either him or Thompson.

“Mayor Gray, (former) mayor Williams, every candidate over the years, has received contributions from Mr. Thompson,” said Orange, adding he has not spoken with Thompson in several months. “I am effective, honest and very focused on what I fight for, so I feel good about my campaign.”

Orange notes he has not received any contributions from Thompson this year, which may give him some distance from Thompson on the campaign trail.

“You have no idea what the scope of this investigation is,” Orange said. “It seems to be a pretty wide net.”

And the issue of sources of campaign contributions could also be tricky ground for Shapiro or Biddle to leverage to a political advantage in a four-person race.

Last year, when he briefly served as an interim council member, Biddle raised $205,000 for his unsuccessful bid for reelection, including from developers and corporate interests.

It does not appear that Biddle collected money from Thompson. At the time, however, Biddle was being supported by Gray and D.C. Council Chairman Kwame R. Brown (D), both of whom are the subject of active federal investigations into their campaigns.

Shapiro also has a lengthy fundraising history in Prince George’s County Council that could became a target for Orange researchers.

But in an interview, Shapiro said he’s “absolutely comfortable with the utmost scrutiny of my campaign contributions in Prince George’s.”

“Vincent Orange has thousands of dollars in questionable contributions. This is something he needs to be accountable to the public for,” Shapiro said.

 The fourth candidate in the race, Holness, said last week she does not accept donations from business interests.