First Lady Michelle Obama and Jill Biden were booed by some NASCAR fans today at Homestead-Miami Speedway in Homestead, Fla.

Obama and Biden had agreed to serve as grand marshals for the Ford 400, the last NASCAR race of the season, to generate publicity for their Joining Forces initiative, which supports military families, Fox News reported.

The crowd cheered as the announcer introduced Sgt. Andrew Berry, a former sniper with U.S. Army in Iran and Afghanistan, and his wife and four sons, who joined Obama and Biden to give the "Gentlemen, start your engines” order.

But when the First Lady and the Vice President’s wife were introduced as grand marshals, boos could be heard from the crowd, the South Florida Sun-Sentinel reported.

Obama and Biden had received a much more appreciative welcome earlier in the day, when they stopped by the pre-race drivers’ meeting and got a standing ovation, The Associated Press reported.

“I know this is a big day for all of you so we’re not going to take up your time because you need to be focused,” Obama told the drivers, according to the AP. “We just wanted to stop by and say thank you. NASCAR has just been amazing in terms of its support not just today, but everyday of military families.”

Obama and Biden also attended a barbeque lunch for service members and their families before the race, the Sun-Sentinel reported.

