Brett Kavanaugh sworn in as Supreme Court justice, despite allegations of sexual assault.

Brett Kavanaugh has been sworn in as a US Supreme Court justice after the bitterly polarised Senate narrowly confirmed him.

The Senate vote delivered an election-season triumph to President Donald Trump that could swing the court rightward for a generation after a battle that rubbed raw the country’s cultural, gender and political divides.

Kavanaugh was quickly sworn in at the court building, across the street from the Capitol, even as protesters chanted outside.

The near party-line Senate vote was 50-48, capping a fight that seized the national conversation after claims emerged that Kavanaugh had sexually assaulted women three decades ago – which he emphatically denied.

Those allegations magnified the clash from a routine Supreme Court struggle over judicial ideology into an angrier, more complex jumble of questions about victims’ rights, the presumption of innocence and personal attacks on nominees.

Acrimonious to the end, the battle featured a climactic roll call that was interrupted several times by protesters in the Senate galleries before Capitol Police removed them. Vice President Mike Pence presided over the roll call, his potential tie-breaking vote unnecessary.

Listen to Mia Freedman and Rachel Corbett unpack everything you need to know about the allegations against Brett Kavanaugh on Tell Me It’s Going To Be OK. Post continues after audio.

Trump, flying to Kansas for a political rally, flashed a thumbs-up gesture when the tally was announced and praised Kavanaugh for being “able to withstand this horrible, horrible attack by the Democrats.”

Democrats hope that the roll call, exactly a month from elections in which House and Senate control are in play, will do the opposite, prompting infuriated women and liberals to oust Republicans.

Republicans hold only a 51-49 Senate majority and therefore had little support to spare.

It was the closest roll call to confirm a justice since 1881, when Stanley Matthews was approved by 24-23, according to Senate records.

The outcome, telegraphed when the final undeclared senators revealed their views, was devoid of the shocks that had come almost daily since Christine Blasey Ford said last month that an inebriated Kavanaugh tried to rape her at a 1982 high school get-together.

Crowds of demonstrators – mostly Kavanaugh opponents – ricocheted around the Capitol’s grounds and hallways, raising tensions, chanting slogans, interrupting lawmakers’ debates, confronting senators and often getting arrested. Capitol Police said 164 were arrested, raising that count in recent days well into the hundreds.

About 100 anti-Kavanaugh protesters climbed the Capitol’s East Steps as the vote approached, pumping fists and waving signs. US Capitol Police began arresting some of them.

Hundreds of other demonstrators watched from behind barricades. Protesters have roamed Capitol Hill corridors and grounds daily, chanting, “November is coming,” “Vote them out” and “We believe survivors.”

When Trump nominated Kavanaugh in July, Democrats leapt to oppose him, saying that past statements and opinions showed he’d be a threat to the Roe v. Wade case that assured the right to abortion. They said he also seemed too ready to rule for Trump in a possible federal court case against the president.

Yet Kavanaugh’s path to confirmation seemed unfettered until Ford and two other women emerged with sexual misconduct allegations from the 1980s.

Kavanaugh replaces the retired Justice Anthony Kennedy, who was a swing vote on issues such as abortion, campaign finance and same-sex marriage.