It's Happened Before
For example, Democratic President Woodrow Wilson nominated two justices in the 1916 election year, both of whom were quickly confirmed by the then Democrat-controlled Senate.
Supreme court vacancies and confirmations in the final year of a term aren't uncommon.It's rare for it to happen when the Presidency and the Senate are controlled by different parties.
How Quickly Can A Nominee Be Confirmed?
McConnell has expressed confidence to Senate Republicans that the body could quickly confirm a nominee to fill the opening left by RBG's passing.
A report issued by the Congressional Research Service during the nomination process of Justice Brett Kavanaugh found that the average amount of time from nomination to confirmation was more than two-months in recent decades. Meaning, many confirmations took longer, but just as many took fewer than two-months.
Some nominations have moved quickly, including Justice John Paul Stevens in 1975. He was confirmed 19 days after he was nominated.
All of the current justices took more than two months to be confirmed to the bench.
Sources: WSJ, US Senate