Washington (CNN) When Sen. Susan Collins, a Republican who supports abortion rights, emerged from her office last month after her first meeting with Judge Brett Kavanaugh, reporters listened closely trying to divine whether she would back President Donald Trump's Supreme Court nominee.

Her vote, in a closely divided Senate, could help to determine not only Kavanaugh's fate, but the future of Roe v. Wade, the historic 1973 opinion that legalized abortion. Although the opinion was decided more than 40 years ago, it remains a lightning rod in modern confirmation hearings as senators on each side of the issue have tried to press nominees to tip their hands.

Abortion opponents hope that Kavanaugh will provide a fifth vote on a court decision to either overturn Roe or weaken the decision. The stakes are high. Kavanaugh has never opined directly on the case, but if confirmed, he will fill the seat of Justice Anthony Kennedy, who was a key swing vote on the issue of abortion restrictions.

To reporters, Collins suggested that she thought Kavanaugh respected Roe because he told her that it was "settled law."

"He said that he agreed with what (Chief) Justice (John) Roberts said at his nomination hearing in which he said it was settled law," Collins said.

Read More