John Dougherty, leader of the politically powerful electricians union, told his members in a letter that a federal investigation that went public on Aug. 5 is as much about them as it is about him.

"Here's the bottom line: If these investigations were simply about me, I'D RETIRE TODAY and save our union any additional headaches, but they're not," Dougherty said in the letter to members of Local 98 of the International Brotherhood of Electrical Workers. "The scope of these investigations suggest a comprehensive attack upon multiple aspects of Local 98."

Dougherty brags in the letter about recent political successes - including electing his brother Kevin to the state Supreme Court and helping to put Mayor Kenney in office - and suggests that is what drew the attention of the FBI and IRS.

The letter went out Friday in advance of a meeting Local 98 held for its members Tuesday night.

A person familiar with the federal investigation said it focuses on the union's finances and its involvement in the political campaigns of Kenney and Kevin Dougherty, along with John Dougherty's finances and taxes.

Local 98 supported Kenney through an independent expenditure political action committee called Building a Better Pennsylvania. Such groups have no campaign finance limits, as long as they do not coordinate efforts with candidates.

The union first used Building a Better Pennsylvania to support U.S. Rep. Brendan Boyle's bid for Congress in 2014.

"Local 98 has had a couple of good years recently, which is another likely reason why we've drawn the government's attention again," Dougherty wrote. "We helped elect Brendan Boyle to the U.S. Congress. We were instrumental in electing three new Justices to the Pennsylvania Supreme Court. We were probably the first and strongest supporters of Jim Kenney for mayor and recently helped him launch his unprecedented 'Rebuild Philadelphia' program."

Dougherty's letter also nods toward a state grand jury investigation, unrelated to the federal probe, launched in February to look into allegations of a pattern of intimidation of contractors by Local 98, according to people familiar with that inquiry.

"We've taken on some of the country's most deep-pocketed, well-connected corporations," Dougherty wrote. "We don't shy away from these high profile disputes. We also recognize that our high profile can bring a harsh light shone upon us."

Dougherty's letter went out two weeks after a large team of FBI and IRS agents raided more than a half a dozen homes and offices in Philadelphia and South Jersey, making public the broad probe.

Agents executed search warrants at Dougherty's house in South Philadelphia, his sister's house next door, Local 98's offices, the Mount Laurel home of union president Brian Burrows, and the City Hall and district offices of Councilman Bobby Henon, who serves as majority leader.

Henon, a former Local 98 political director, remains on the union's payroll in an untitled position reporting to Dougherty.

Dougherty, in his letter, tells his union's members "I want to assure all of you that it's business as usual at Local 98."

"We are vigorously defending our union's good name and have retained the finest legal minds in the city to protect us," Dougherty wrote.