After a dull run-up to the election, Supreme Court Justice Ruth Bader Ginsberg has died. This is almost certainly far too close to the election to permit Trump to select and ram through a new Justice; the Dems would certainly do everything in their power to squash any such nomination process. If Trump makes a nomination prior to the election and the process gets underway, the Dems will certainly maneuver things to push off the certification until after the election. if Trump wins, they might just give up in dismay and allow the process to continue; if Harris wins, they will certainly go apoplectic in their efforts to kill the process prior to the inauguration.
Consequently: the selection of a Justice to replace the far left extremist (notably, she came down on the wrong side of history in the Heller decision) Ginsberg will be a top priority for the parties.