From this Washington Post oped:

The records of these 16 cases have become all the more important because of publicly released information about Roberts’s policy views during an earlier time. As a young but high-ranking political appointee in the Reagan administration, Roberts was involved in, among other things, setting policy on issues of civil rights — including those as fundamental as the right to vote and to be free from discrimination based on race, gender, national origin and disability. If Roberts continues to hold the views he appears to have expressed in the early 1980s, then his views on civil rights are out of the mainstream, and the people have the right to know that.
Specifically, and contrary to the intent of overwhelming majorities in both the House and the Senate, it appears that Roberts proposed a very narrow and crabbed interpretation of the Voting Rights Act that would essentially eviscerate the meaning of that law. Fortunately, his view did not prevail. But if a nominee to the Supreme Court believes in such a strained and narrow interpretation of such a fundamental right, then I believe he is not qualified to serve in that important position. The information we have requested from the administration would give us a more in-depth understanding of Roberts’s views on this key civil rights issue, and we are entitled to it.