In the letter to committee chair Chris Coons (D-Del.) and vice chair James Lankford (R-Neb.), CfA executive director Michelle Kuppersmith accused Blackburn of violating Senate rules prohibiting favorable treatment for lawmakers by law enforcement.

On her way out of the Capitol complex last month, Blackburn was pulled over by Capitol Police, flashed her pin, jumped back in the car and said “drive,” CNN reported based an anonymous source and texts from a Blackburn aide, who reportedly told friends the officer “didn’t say a word, just shook his head.”

Blackburn’s office confirmed that version of events to CNN but said she was complying with a request from the officer for identification – though Kuppersmith alleged that claim “does not ring true,” noting that Blackburn was the passenger and that, typically, police would ask the driver for identification.

Capitol Police told CNN they did not have documentation of the incident.

Kuppersmith called on the committee to investigate the incident, and her “untruthful” statements to the media about it, and “make clear” to Blackburn that it was “impermissible and reflects discreditably on the Senate.”

Forbes has reached out to Blackburn’s office and the Capitol Police for comment.