BOSTON (AP) -- The Republican senator who suddenly sits at the center of the explosive Supreme Court debate vowed Monday to ensure the FBI does "a real investigation" into President Donald Trump's nominee as he trekked across New England while exploring a possible run for president.
"It does us no good to have an investigation that just gives us more cover," Arizona Sen. Jeff Flake told hundreds of young people at the Forbes Under 30 Summit.
Flake's comments come as the White House insisted it's not "micromanaging" the new one-week review of decades-old allegations of sexual misconduct against Supreme Court nominee Brett Kavanaugh. Some Democratic lawmakers claimed the White House was keeping investigators from interviewing certain witnesses.
Flake delivered the message at a Boston conference hours before he faced New Hampshire voters for the second time this year. The 55-year-old Republican, who is retiring from the Senate at the end of the year, has already declared his interest in a possible 2020 presidential bid - as a Republican or an independent - in part to stop Trump from winning a second term.
Three days ago, Flake single-handedly delayed Kavanaugh's confirmation proceedings by insisting on an FBI investigation as a condition for his support.
He told CBS' "60 Minutes" on Sunday that the conservative judge's nomination would be "over" if federal investigators determine he lied to the committee.
Flake, a lifelong conservative has quickly emerged as the centerpiece of a passionate lobbying effort from the right and left.
Organizers of the Boston event said they moved the location to City Hall after security concerns emerged about the original location.
Hundreds of liberal protesters, victims of sexual assault among them, pleaded with Flake to block Kavanaugh's nomination outside the venue. A similar demonstration was planned for New Hampshire.
New York congressional candidate Alexandra Ocasio-Cortez warned Flake and other elected leaders that voters would end their careers should they support Trump's Supreme Court nominee.
"We are going to keep pushing because justice in America is not just about protecting the powerful," Ocasio-Cortez charged. "It is about uplifting the voices that have been victimized."
Boston Mayor Marty Walsh offered a direct message to the Republican senator from Arizona.
"I guess I want to say, 'Thank you,'" Walsh said. "But that's your job. That's your job to vet the nominee."
The true test for Flake would come once the full Senate votes on the Kavanaugh nomination in the coming days, Walsh said.
"He has an opportunity to do something very special at some point next week," the mayor said.
Flake was set to address New Hampshire voters later in the day.
In March, Flake told New Hampshire Republicans that someone needs to stop Trump in the 2020 presidential contest. Flake said he may run - either as a Republican or an independent - if no one else does.
"It has not been in my plans to run for president, but I have not ruled it out," Flake said at the time.
"I hope that someone does run in the Republican primary, somebody to challenge the president," Flake said. "I think that the Republicans want to be reminded what it means to be a traditional, decent Republican."
AP writer Bob Salsberg contributed to this report.