"Chairman Graham promised, quote, 'If an opening comes in the last year of President Trump's term, and the primary process has started, we'll wait until after the next election.' Republicans should honor this word, for their promise, and let the American people be heard," Feinstein said, sitting feet away from the Graham.
Democratic senators are outraged after Republicans raced full-tilt to fill the Supreme Court seat vacated by the death of liberal Justice Ruth Bader Ginsburg.
Senate Republicans blocked a nominee put forward by President Barack Obama to fill the late Justice Antonin Scalia's seat in 2016, claiming at the time that it would be wrong to do so in the midst of an election year.
Now, the same party is pushing to confirm a new justice and cement a 6-3 conservative majority on the court less than a month before Election Day.
Feinstein and other Democrats have pointed to what they say is Republican hypocrisy.
"Simply put, I believe I believe we should not be moving forward on this nomination. Not until the election has ended and the next president has taken office," she said.