By Richard Cowan and Lisa Lambert
WASHINGTON (Reuters) - A Republican U.S. senator who could be pivotal in determining whether President Donald Trump's nominee Brett Kavanaugh gets to sit on the Supreme Court raised concerns on Tuesday about the judge's "partisan" tone at last week's hearing into sexual misconduct allegations.
As the FBI completed interviews with four people as part of its one-week investigation into the allegations against Kavanaugh, moderate Republican Senator Jeff Flake said he was worried about the judge's performance before the Senate Judiciary Committee last Thursday.
"I was very troubled by the tone of the remarks. ... The interaction with the members was sharp and partisan, and that concerns me," Flake.
"I tell myself, '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," Flake told an event in Washington hosted by The Atlantic magazine.
Kavanaugh struck an angry and defiant tone during the hearing, denying allegations made by three women against him. He lashed out at Democratic senators and frequently interrupted them, while accusing Democrats of orchestrating a political "hit" against him.
Flake, who is retiring as a senator in January, is seen as potentially key figure in any vote in the full Senate on whether to confirm Kavanaugh.
A member of the Judiciary Committee, Flake voted to approve Kavanaugh in the panel's vote on Friday that sent the nomination to the full Senate for consideration, but only after he requested that the FBI conduct an investigation of the sexual misconduct allegations against the nominee.
Christine Blasey Ford, a university professor from California, testified that Kavanaugh, a conservative federal appeals court judge, sexually assaulted her at a party in 1982 when they were high school students in Maryland.
Supreme Court nominations require Senate confirmation. Trump's Republicans control the Senate by a 51-49 margin. That means if all the Democrats vote against Kavanaugh, Trump could not afford to have more than one Republican oppose his nominee, with Vice President Mike Pence casting a tie-breaking vote.
The nomination has become a politically explosive issue just weeks before Nov. 6 elections, when control of Congress is at stake. Some Republicans fear that pushing ahead with confirmation could alienate women voters, while Democrats seek to capitalise.
Flake said the FBI had completed interviews with four people. ABC News reported that the agency finished its interview with Kavanaugh's friend, Mark Judge, who Ford identified as a witness to the assault. Judge has previously denied any memory of any such incident.
(Reporting by Richard Cowand and Lisa Lambert; Writing by Alistair Bell; Editing by Will Dunham)