Democratic Sen. Chris Coons helped convince his close friend, Republican Sen. Jeff Flake, to push for an FBI investigation into Brett Kavanaugh last week.

But as the Senate prepares to vote on Kavanaugh's nomination on Friday, Coons said he doesn't know which way Flake will be voting.

Democratic Sen. Chris Coons, who helped broker a deal with Republican Sen. Jeff Flake that led to an expanded FBI background investigation of Supreme Court nominee Brett Kavanaugh, says he doesn’t know how Flake or the other undecided senators will vote.

Coons, of Delaware, told ABC’s "Good Morning America" Friday that his undecided friends are not returning his phone calls, "and that typically is a way a senator tells you they’re busy deciding."

"I think this will be very close and we'll have to find out later today when we vote," he added.

—Good Morning America (@GMA) October 5, 2018

The Senate is poised to take a crucial vote Friday on whether to advance Kavanaugh’s nomination amid his denials of allegations of sexual misconduct when he was in high school and college.

Flake, of Arizona, and two other Republican senators (Lisa Murkowski of Alaska and Susan Collins of Maine) have not announced how they’ll vote. Neither has Democrat Joe Manchin of West Virginia.

Republican Senate Judiciary Committee Chairman Chuck Grassley said on Fox News’ "Fox & Friends" he doesn’t yet know how the vote will come out but respects his fellow senators’ decision to keep quiet as they consider what to do.