"It shouldn't be paid for by people that you oversee," Gillibrand told Duffy.
Duffy then noted that Gillibrand's campaign has received $7 million in political contributions from law firms and attorney groups.
But Gillibrand said her donations had "nothing to do with" the topic at hand.
"This hearing is about you and this administration," Gillibrand told Duffy. "This hearing, you are the witness. I am not the witness."
Duffy accused Gillibrand of flying private, eating steak dinners and vacationing on the dime of law firms and legal groups.
Gillibrand denied ever having flown private. However, in 2022, Gillibrand spent the second most in Congress on chartered flights, according to Newsweek. The senator's office did not immediately respond to a request for comment from Fox News Digital.
In both exchanges, Duffy defended his participation in "The Great American Roadtrip," arguing it is about bringing Americans together.
"As we can see from this hearing, there's a lot of partisanship in America," Duffy said. "Seeing your country, experiencing your country through the window of a car is a beautiful thing. It actually unites America."