With centrist senators still undecided on his Supreme Court nomination, Brett Kavanaugh made his closing argument by insisting he was an "independent, impartial judge" whose impassioned testimony "reflected my deep distress at the unfairness" of the accusations against him.

In an opinion piece published by the Wall Street Journal, Kavanaugh conceded that some of his testimony - which delighted President Donald Trump - was over the top. The article appeared to be carefully aimed at wavering senators, particularly Sen. Jeff Flake, R-Ariz., who has lamented Kavanaugh's demeanor.

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Kavanaugh's decision to pen the article - an unprecedented move by a Supreme Court nominee - was a last gamble before a looming procedural vote in the Senate, scheduled for 10.30am Friday.

As sexual assault allegations have remained uncorroborated, Democrats have increasingly shifted the ground to questions over Kavanaugh's truthfulness about drinking and what Cory Booker, D-N.J., has described as "the temperament issue."

Kavanaugh wrote: "I was very emotional last Thursday, more so than I have ever been. I might have been too emotional at times. I know that my tone was sharp, and I said a few things I should not have said. I hope everyone can understand that I was there as a son, husband and dad.

"At times, my testimony — both in my opening statement and in response to questions — reflected my overwhelming frustration at being wrongly accused, without corroboration, of horrible conduct completely contrary to my record and character," he wrote. "My statement and answers also reflected my deep distress at the unfairness of how this allegation has been handled."

On Tuesday, Flake said that Kavanaugh's "interaction with the members was sharp and partisan and that concerns me". He added: "You give a little leeway because [of] what he’s been through. But on the other hand, we can’t have this on the court. We simply can’t."

[Related: Retired Justice John Paul Stevens: Kavanaugh disqualified from serving on Supreme Court after Senate hearing]

Democrats have lambasted Kavanaugh for his angry and hard-edged testimony last Thursday following the testimony of Christine Blasey Ford, who accused him of sexually assaulting her at a teenage party in the Maryland suburbs in the summer of 1982.

He told senators: "This whole two-week effort has been a calculated and orchestrated political hit, fueled with apparent pent-up anger about President Trump and the 2016 election, fear that has been unfairly stoked about my judicial record, revenge on behalf of the Clintons and millions of dollars in money from outside left-wing opposition groups."

In his article, the federal judge said the person he was before the Senate committee would not be the judge he would be on the country's highest court. He vowed to be "even-keeled" in his handling of cases if confirmed by the Senate, as he stated he had been throughout his 12 years as a judge.

Sen. Dianne Feinstein, D-Calif., the ranking Democrat on the Senate Judiciary Committee, said last Friday Kavanaugh's behavior and defense to multiple allegations of sexual misconduct was "aggressive" and "belligerent."

"I have never seen a nominee for any position behave in that manner," Feinstein said during a committee meeting, according to a report. "Judge Kavanaugh used as much political rhetoric as my Republican colleagues, and what's more, he went on the attack."

Kavanaugh responded in his hearing to allegations by California professor Christine Blasey Ford, who had testified earlier in the day. Ford has accused Kavanaugh of pinning her down, covering her mouth, and trying to remove her clothes during a party while the two were in high school more than 30 years ago.

Following those hearings, the committee voted 11-10 along party lines to send Kavanaugh's nomination to the full Senate. Thursday's op-ed comes as senators are reviewing a supplemental FBI background investigation into Ford's accusations against Kavanaugh ahead of a final vote.

Sen. Richard Blumenthal, D-Conn, described Kavanaugh's appearance before the Senate as "angry, vengeful, self-pitying and threatening." He told CNN the article was "a pretty obvious effort to clean up the debacle of his testimony."