Sen. Kamala Harris said Wednesday that busing students should be considered by school districts trying to desegregate their locations — not the federal mandate she appeared to support in pointedly criticizing rival Democratic presidential candidate Joe Biden last week.

Harris had a breakthrough moment at the candidates’ first debate when she criticized Biden for his opposition to mandatory school busing when he was a senator in the 1970s. Harris said she benefited from busing as an elementary school student in Berkley, California, in the early 1970s.

“That’s where the federal government must step in,” Harris said, looking at Biden and winning a burst of applause from the auditorium in Miami.

On Wednesday, though, Harris characterized busing as a choice local school districts have, not the responsibility of the federal government.