So this happened in February 2016: Justice Scalia died. And unexpectedly, President Obama got the opportunity to nominate another judge to the Supreme Court.
How did the Republicans respond? Within minutes, the battle lines were drawn with warnings that President Obama should not be doing so because his mandate was stale. They then escalated the threat to a new level: they refused to even consider anyone President Obama would nominate. Forget confirmation hearings, they vowed to not even meet with him.
Heck, Mitch paid him a personal visit to tell him that: