Sure they can.
President-elect Biden and incoming Majority Leader Schumer can announce that if McConnell jams through Trump’s pick in a lame duck, their first order of business in January will he adding 2 seats to the Supreme Court.
IS IT POSSIBLE JOE BIDEN wins the presidency, Republicans lose the Senate and MCCONNELL jams through the nominee in the lame duck? Yes, you bet. Can Democrats do anything besides bellyache? No. They can’t.