The O’Connell rule is being misrepresented by the left. At one point it was the Biden rule.
It was that before an election, a supreme court vacancy would not have an appointment if the presidency and the Senate were held by opposite parties. If they were the same party, an appointment would be made.
When Obama was president, the Senate was held by the opposite party – the Republicans. Therefore no appointment was voted on.
The situation now is the presidency and the Senate are held by the same party, so an appointment will be voted on before the election.