US president Donald Trump has denounced Democratic efforts to block Brett Kavanaugh’s Supreme Court confirmation as a cynical “con job” and launched a dismissive attack on a second woman accusing the nominee of sexual misconduct in the 1980s.

Senate Majority Leader Mitch McConnell predicted that Mr Kavanaugh would win approval, despite the new allegations and uncertainty about how pivotal Republicans would vote in a roll call now expected early next week.

Like much of America, politicians awaited a momentous Senate Judiciary Committee hearing in which Mr Kavanaugh and chief accuser Christine Blasey Ford are to testify on Thursday, though not together.

Committee chairman Chuck Grassley said Arizona prosecutor Rachel Mitchell would be brought in to handle questioning of Mr Kavanaugh and Ms Ford.

Senate Majority Leader Mitch McConnell
Senate Majority Leader Mitch McConnell (AP Photo/Andrew Harnik)

Ms Mitchell comes from the Maricopa County Attorney’s Office in Phoenix, where she is the chief of the Special Victims Division, which covers sex crimes and family violence.

Hanging in the balance is Mr Trump’s chance to swing the high court more firmly to the right for a generation. Despite Mr McConnell’s forecast that Republicans will “win”, Mr Kavanaugh’s fate remains uncertain in a chamber where Republicans have a scant 51-49 majority.

Hoping the hearing will yield no new surprises, the Senate Judiciary Committee scheduled its own vote on Mr Kavanaugh for Friday, and Republican leaders laid plans that could keep the full Senate in session over the weekend and produce a final showdown roll call soon after — close to the October 1 start of the high court’s new term.

Given that the Judiciary Committee’s GOP members are all male, Mr McConnell said the panel was hiring a “female assistant” to handle the questioning for Republicans “in a respectful and professional way”.

Mr Grassley identified Ms Mitchell in a press release late on Wednesday, describing her as “a career prosecutor with decades of experience prosecuting sex crimes”.

Each senator on the 21-member panel will be allowed five minutes to ask questions, said committee spokesman Taylor Foy.

Meanwhile, the Republicans were still assessing what Mr Kavanaugh’s interview on Monday on the Fox News Channel — an unusual appearance for a Supreme Court nominee — indicates about how he would do in Thursday’s hearing.

Brett Kavanaugh, with his wife Ashley Estes Kavanaugh, answers questions during a Fox News interview
Brett Kavanaugh, with his wife Ashley Estes Kavanaugh, answers questions during a Fox News interview (AP Photo/Jacquelyn Martin)

During the interview, Mr Kavanaugh denied sexually assaulting anyone. He also denied the account of a second woman, Deborah Ramirez.

Mr Kavanaugh’s accounts of his behaviour in high school and college have faced intense scrutiny, with some of his former classmates coming forward to challenge his claims.

James Roche, a Yale graduate who says he was Mr Kavanaugh’s roommate in 1983, issued a public statement saying he was “close friends” with Ms Ramirez and “cannot imagine her making up” the story about Mr Kavanaugh exposing himself.

While a few Republicans have strongly challenged the credibility of Mr Kavanaugh’s accusers, Mr Trump’s words have been more biting.

Last week, he lampooned Ms Ford’s allegation that an inebriated Mr Kavanaugh trapped her beneath him on a bed at a high school house party and tried to take her clothes off before she escaped. Surely she would have reported it to police if the encounter was “as bad as she says”, the president said.

“It’s a con game they’re playing,” he said. “They’re really con artists. They don’t believe it themselves, OK?”

Supreme Court Kavanaugh Trump
President Donald Trump launched a dismissive attack on a second Kavanaugh accuser (AP Photo/Evan Vucci)

Mr Trump’s latest broadside was aimed at Ms Ramirez, who conceded to The New Yorker that she had been drinking at the time she says Mr Kavanagh exposed himself. She also said she was uncertain of some details.

“The second accuser has nothing,” Mr Trump told reporters at the United Nations. “The second accuser doesn’t even know — thinks maybe it was him, maybe not. She admits she was drunk. She admits time lapses.”

In a phone call with Judiciary Committee staff of both parties, Mr Kavanaugh denied Ms Ramirez’s story, panel spokesman Mr Foy said.

Ms Ramirez’s lawyer, John Clune, said his client stood by The New Yorker story and said he and Mr Grassley’s committee were trying to decide how to provide more information to the panel.

He said an FBI investigation “is the only way to get the truth”.