The Caucus first reported on the investigation that is being led by Inspector General Bruce Beamer.
Stack and his wife are accused of verbally abusing their security detail and staff at the LG’s mansion.
The investigation will test the strength of an already tenuous relationship between Wolf and Stack.
Since Governor and Lieutenant Governor are nominated separately, Wolf and and Stack were forced onto the same ticket in 2014. During the campaign that year, Wolf and Stack barely campaigned side-by-side, only making one campaign appearance together.
Since taking office, the two have not grown closer, continuing to shy away from joint appearances.
Depending on the results of the investigation, it could open the door to a primary challenge for Stack.
PoliticsPA has reached out to Lieutenant Governor Stack’s office for comment.