"It is only through partisan political glasses that his qualifications become questionable."
We aren't talking about qualifications; we are talking about character. Someone can be a sitting judge and not be "qualified" to be one. Take for example the case of Judge Kosinski, Kavanagh's mentor and current friend:
Federal Judge Alex Kozinski Retires Abruptly After Sexual Harassment Allegations
During the confirmation hearings, Kavanaugh was asked about Kozinski and said he knew nothing of his mentor's disqualifiying behavior. I hope he is telling the truth. The Intercept did a story on potential whistleblowers who want to come forward contesting his claim. I posted a link to the story, which hasn't gotten any traction either on here or in the world at large:
Attorney Sent Letter to Grassley/Feinstein About Kavanaugh
The top Republican and Democrat on the Senate Judiciary Committee were both approached in July by an attorney claiming to have information relevant to the confirmation of Brett Kavanaugh to the Supreme Court. The attorney claimed in his letter that multiple employees of the federal judiciary would be willing to speak to investigators, but received no reply to multiple attempts to make contact, he told The Intercept. Cyrus Sanai made his first attempt to reach out to Sens. Charles Grassley, R-Iowa, and Dianne Feinstein, D-Calif., in a letter dated July 24. Sanai told the committee leadership that "there are persons who work for, or who have worked for, the federal judiciary who have important stories to tell about disgraced former Chief Judge Alex Kozinski, and his mentee, current United States Supreme Court nominee Brett Kavanaugh."
"I know that there are people who wish to speak out but fear retaliation because I have been contacted by more than a half-dozen such persons since Judge Kozinski resigned in disgrace."
Sanai is the California attorney who blew the whistle on Kozinski years before a series of articles in the Washington Post in December finally brought about the resignation of the former chief judge of the 9th Circuit Court over sexual harassment revelations. Sanai has long challenged the judiciary and was deemed a "vexatious litigant" by one trial court, an attempted designation that was overturned on appeal.
I think covering up for another judge's bad behavior would be a disqualification for being on the SC (or any court), but unless and until any potential whistleblowers come forward, we can't say Kavanaugh did that.