School busing has for decades been a contentious tool for racial integration. And it is back in the spotlight 65 years after Brown v. Board of Education, the Supreme Court’s landmark decision to desegregate public schools, because Senator Kamala Harris of California recently attacked former Vice President Joseph R. Biden Jr. for his position on busing.

Since the issue resurfaced in June in the first set of Democratic presidential debates, The New York Times has unearthed and reviewed more than four decades of Mr. Biden’s voting record and statements about the issue. You can read the full result of that investigation here. Below is a brief timeline of highlights.

A Turning Point

1974: Mr. Biden, who was then a senator for Delaware, voted two times to protect court-ordered busing to achieve desegregation, including the decisive vote on an amendment that would have effectively done away with it.

But months after an angry crowd in a school auditorium criticized him for that vote, Mr. Biden said in a speech on the Senate floor that he had become “more and more disenchanted with busing as a remedy.”