WEST DES MOINES, Iowa (AP) 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 Berkeley, California, in the early 1970s.

Thats 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.

Busing, while not central to the Democratic primary, has become a proxy issue for the debate between Biden and Harris over race as well as broader questions about whether the 76-year-old former vice president is out of step with his party.

After a Democratic Party picnic Wednesday in West Des Moines, Harris was asked by reporters whether she supports federally mandated busing.

I think of busing as being in the toolbox of what is available and what can be used for the goal of desegregating Americas schools, she responded.

Asked to clarify whether she supports federally mandated busing, she replied, I believe that any tool that is in the toolbox should be considered by a school district.

In a tweet Wednesday, Biden deputy campaign manager Kate Bedingfield knocked Harris for her response, writing, Its disappointing that Senator Harris chose to distort Vice President Bidens position on busing particularly now that she is tying herself in knots trying not to answer the very question she posed to him!

Harris comments Wednesday were far from the indictment she delivered during the debate last week.

Under attack on the debate stage, Biden appeared stunned and dismissed Harris comments as a mischaracterization of his positions. He has notably begun his remarks to fundraisers by talking about how civil rights spurred his entry into public life more than 45 years ago.

To be sure, Bidens record on busing is complicated.

Biden has insisted he only opposed busing ordered by the federal Education Department, and said allowing local governments and school districts to implement busing was one of the things I argued for at the time.

During an appearance at a conference last week in Chicago, Biden told the audience he never, never, never, ever opposed voluntary busing.

But Biden was an outspoken opponent of federally mandated busing in the 1970s and 80s, sponsoring a congressional measure that would have limited funding for federal busing efforts.

The issue spilled into Iowa as Harris and Biden returned Wednesday for the first time since the debate. Both will need some success in Iowas leadoff nominating caucuses to build momentum heading into South Carolina, the first Southern primary, where they are vying aggressively for a robust African American voting bloc.

Biden and Harris also have been aggressively courting members of the Congressional Black Caucus, with Harris edging Biden in endorsements, picking up support from Reps. Bobby Rush of Illinois and Frederica Wilson of Florida. Biden last week landed the support of popular Atlanta Mayor Keisha Lance Bottoms.

In Iowa, where African Americans are a small minority, endorsements from black leaders are magnified. Harris got the backing of two popular black ministers after her debate performance last week.

Appearing Wednesday evening in Waterloo, Iowas most densely African American city, Biden received the backing of one of that citys most influential black ministers.

Beaumont contributed from Waterloo, Iowa.