"For weeks, I have stated that I would not support taking up a potential Supreme Court vacancy this close to the election. Sadly, what was then a hypothetical is now our reality, but my position has not changed," the Alaska Republican said in a statement.
"I did not support taking up a nomination eight months before the 2016 election to fill the vacancy created by the passing of Justice Scalia. We are now even closer to the 2020 election -- less than two months out -- and I believe the same standard must apply."
Murkowski did not address whether she will oppose President Donald Trump's nominee in a lame-duck session if Joe Biden wins the presidency.
Should two more Republican senators also say they oppose movement on Trump's forthcoming nominee, Democrats will have enough support to punt the nomination to the lame-duck session.
This story is breaking and will be updated.