Responding to the senator's questions, Buescher confirmed that he has been a member of the Knights since he was 18 years old, noting that his membership "has involved participation in charitable and community events in local Catholic parishes."
"I do not recall if I was aware whether the Knights of Columbus had taken a position on the abortion issue when I joined at the age of 18," he wrote in response.
Harris raised a statement from Supreme Knight Carl A. Anderson, who said that abortion constituted "the killing of the innocent on a massive scale" and asked Buescher if he agreed with Anderson.
Buescher said he was not responsible for drafting statements or policies made by the Knights and that, as a federal judge, he would consider himself bound by judicial precedent regarding abortion.
"I did not draft this language. If confirmed, I would be bound by precedent of the United States Supreme Court and the Eighth Circuit Court of Appeals and would not be guided by statements made by others," Buescher told the senator.
Blomquist told CNA that asking a judicial nominee to defend his membership of a major Catholic charitable organization is disturbing.
"We believe that membership in the Knights of Columbus, which helps everyday men put their Catholic faith into action, is worthy of commendation and not something a nominee for public office should be asked to defend," she said.
In 2014, Buescher ran as a candidate in the Republican primary election for Nebraska attorney general. During that campaign he described himself as "avidly pro-life" and said that opposition to abortion was part of his "moral fabric."
Senator Cory Booker (D-NJ) noted the nominee's previously outspoken opposition to abortion and asked "why should a litigant in your courtroom expect to get a fair hearing from an impartial judge in a case involving abortion rights?"
Buescher responded that "as a candidate for Nebraska Attorney General in 2014, I did what candidates for any major state or federal office do, which is to take political positions on a variety of issues of the day."
"However, there is a difference between taking political positions as a candidate for elective office and serving as a federal judge. I believe a judge's role and obligation is to apply the law without regard to any personal beliefs regarding the law," Buescher wrote.
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"If confirmed, I will faithfully apply all United States Supreme Court and Eighth Circuit Court of Appeals precedent on all issues, including Roe v. Wade."
Buescher also fielded questions from senators about Trump administration policy on Title X funding for clinics providing abortions and referrals, as well as on the application of anti-discrimination law to questions related to gender identity or sexual orientation.
The nominee underscored that, as a judge, it was not for him to advance personal or political opinions but to make fair and impartial rulings based on the law and judicial precedent.
If confirmed by the Senate, Buescher will fill the vacancy left by Judge Laurie Smith Camp, who assumed senior status - a kind of judicial semi-retirement - on Dec. 1.
This story has been updated.