It's not enough that Lt. Gov. Mike Stack III doesn't have the public support of the incumbent governor, and he's facing an eye-popping six primary opponents. What's more, Stack's legal bills are piling up — and one of his biggest campaign contributors is his mom.

Stack, an heir to one of Philadelphia's entrenched Democratic political families, spent more than $80,000 in legal fees last year, according to campaign-finance records made public last week. Stack's report didn't give an explanation, but he made the payments as the state inspector general investigated allegations that the lieutenant governor and his wife mistreated their state security detail and other staff.

Stack owed an additional $21,479 to the Philadelphia law firm Montgomery McCracken Walker & Rhoads LLP, the records show. Stack retained Mark Sheppard, a white-collar criminal defense attorney with the firm, to represent him in the inspector general's probe last year.

In total, Stack's legal fees ate up about 30 percent of the $338,000 he raised last year.

The heavy spending comes as a half-dozen Democrats, sensing a vulnerable incumbent, are challenging Stack for the party's nomination in May. That's an unusually big pool of contenders for a relatively obscure statewide office. It pays an annual salary of $162,373.

Gov. Wolf, a Democrat who is up for reelection in November, hasn't endorsed a candidate in the race. "Gov. Wolf and I have different styles," Stack said during a debate last week. "I'm from Philadelphia. He's from York. But we have been active partners on a number of issues. We are in lock-step on every major issue that Pennsylvanians care about."

In April, Wolf took the extraordinary step of stripping the Stacks of their state police protection and scaled back staff at their official residence outside Harrisburg. Stack's office later said his wife, Tonya, had checked into a treatment facility to get help for a mental-health problem.

Wolf has said he won't release the inspector general's report, in part citing Tonya Stack's treatment.

Marty Marks, a spokesman for Mike Stack, said the legal expenses wouldn't hamper the campaign. "We're confident we'll raise the money we need to run an effective and winning campaign," Marks said.

Although Stack raised the most money last year of any Democratic candidate for lieutenant governor, one of his rivals ended the year with more cash on hand. State Rep. Madeleine Dean, of Montgomery County, had $270,000 — about $40,000 more than Stack.

Braddock Mayor John Fetterman had about $110,000. Also running are Chester County Commissioner Kathy Cozzone, Lancaster County Commissioner Craig Lehman, and Aryanna Berringer, an Army veteran and IT manager.

Among Stack's most generous contributors was his mother, Felice R. Stack, a retired municipal court judge. She lent her son $60,000. "I guess she likes her son," said Marks, the campaign spokesman, when asked about the loan.

Stack also received $25,000 from Fumo for Senate, the political action committee affiliated with Vince Fumo, the former state senator from South Philly who went to prison for public corruption.

That was Fumo for Senate's only donation last year. The PAC also lent $30,000 to State Sen. Larry Farnese's political action committee.

"It is no secret that I have, and will continue to, support both Mike and Larry," Fumo said in an email. "They are both terrific Public Servants. In fact, I believe that they are in the top 5 percent of elected officials who represent Philadelphia and are both doing great things for the city. I successfully helped to elect each of them to win when they first ran."