Brett Kavanaugh was sworn in as the 114th justice of the US Supreme Court on Saturday, after a wrenching debate over sexual misconduct and judicial temperament that shattered the Senate, captivated the nation and ushered in an acrimonious new level of polarisation — now encroaching on the court that the 53-year-old judge may well swing rightward for decades to come.

Even as Kavanaugh took his oath of office in a quiet private ceremony, not long after the narrowest Senate confirmation in nearly a century and a half, protesters chanted outside the court building across the street from the Capitol. The two-vote margin of victory made it the closest Supreme Court confirmation vote since 1881 — and by far the most contentious since Clarence Thomas in 1991.

"This is a historic night," Trump told supporters at a rally in Kansas after signing Kavanaugh's commission aboard Air Force One.

"I stand before you today on the heels of a tremendous victory for our nation, our people and our beloved Constitution."

Trump will host Kavanaugh at the White House for a public swearing-in ceremony on Monday, following Saturday's formal oath-taking at the high court.

Victory for Republicans

The climactic 50-48 roll call capped a fight that seized the national conversation after claims emerged that he had sexually assaulted women three decades ago — allegations he emphatically denied. Those accusations transformed the clash from a routine struggle over judicial ideology into an angry jumble of questions about victims’ rights, the presumption of innocence and personal attacks on nominees.

His confirmation provides a defining accomplishment for President Donald Trump and the Republican Party, which found a unifying force in the cause of putting a new conservative majority on the court. Before the sexual accusations grabbed the Senate’s and the nation’s attention, Democrats had argued that Kavanaugh’s rulings and writings as an appeals court judge raised serious concerns about his views on abortion rights and a president’s right to bat away legal probes.

Democratic senators, who worked to block Kavanaugh, insisted the caustic battle would motivate their party faithful at the polls next month.

"It is a sad day, but the recourse will have to be on election day," Democratic Senator Amy Klobuchar told reporters.

Senator Lisa Murkowski, the only Republican to oppose Kavanaugh, said it was time for the Senate — and Americans — to "heal" after such a divisive few weeks.

She acknowledged the anguish of the protesters who interrupted the historic Senate vote, telling reporters afterwards: "I was closing my eyes and praying — praying for them, praying for us and praying for the country."