The US Senate, controlled the Republican Party, is expected to vote to confirm Mr Kavanaugh’s appointment to the Supreme Court.
The conservative judge has been embroiled in a fierce row over historic allegations of sexual misconduct, which he denies.
Today’s vote will boost Donald Trump‘s drive to secure conservative dominance of the United States’ highest court.
But critics fear Mr Kavanaugh’s judicial stance could damage gay rights, abortion rights and protections for immigrants.
Chuck Schumer, the Democratic Senate minority leader, branded Mr Kavanaugh an “extreme partisan” with an “injudicious demeanour”.
In a furious attack on the judge, he said: “When the history of the Senate is written, this will be a flashing red warning light.
“Truly, this confirmation vote is a low moment for the Senate and the country.”
“This grossly unfair, biased process is about to elevate a nominee who doesn’t belong on the nation’s highest bench.”
Hundreds of protesters against Mr Kavanaugh assembled on the grounds of the Capitol and at the Supreme Court earlier today.
They chanted, “Vote them out! Vote them out!” and carried signs including “I am a survivor, not a troublemaker!”
But Mr Trump doubled-down on his backing for Mr Kavanaugh and pointed to a counter-protest held to support the judge.
He tweeted: “Women for Kavanaugh, and many others who support this very good man, are gathering all over Capitol Hill in preparation for the vote.
“It is a beautiful thing to see – and they are not paid professional protesters who are handed expensive signs. Big day for America!”
Kavanaugh is a well-known figure in Washington and has been involved in some of the biggest controversies of the past two decades.
He worked for independent lawyer Ken Starr during the impeachment of Democratic former President Bill Clinton in the late 1990s.
He was also on Republican George W. Bush’s team in the contentious Florida recount fight in the 2000 presidential election.
US Senate Republican leader Mitch McConnell said the row over Mr Kavanaugh’s confirmation will help his party retain control of the Senate.
Speaking ahead of the US midterm elections, Mr McConnell told Reuters: “Nothing unifies Republicans like a court fight.
“It’s been a seminal event leading into the fall election.”
Addressing the intensity of the opposition from protesters and Democrats, McConnell said: “We’ve literally been under assault by the mob.”
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