KOB-TV in Albuquerque reported that Unser, a two-time winner of the Indianapolis 500, was named as one of two extortion victims in a 137-count indictment against 47-year-old Bobby McMullin.
The suspect runs a local strip club and was arrested last May.
Police allege McMullin ran an Internet escort service that actually was a prostitution ring.
The DA's office told the station McMullin allegedly asked Unser for $750,000 or he would release a tape showing Unser in a compromising video tape to the public.
Prosecutors say the tape is not connected to the suspected prostitution ring.
Unser has had problems in the past, including a 2002 arrest for an alcohol-fueled fight with a girlfriend, and a 2007 arrest for a DWI hit-and-run.
The DA's office did not say if Unser's past arrests made him an easy mark.