A special election almost certainly would benefit Republicans, NOT Democrats.
The current situation is VERY BAD for Republicans and a GREAT SITUATION for Democrats. Democrats are the ones who should not want a special election. Republicans should want McConnell gone ASAP. An incapacitated McConnell means Republicans have only 52 votes in the Senate instead of 53. With only 52 votes, now only 3 Republicans need to vote with Democrats to kill any legislation or nominees. For example, Democrats now need only 3 Republicans to vote against Blanche as AG to kill his nomination. With McConnell present or another Republican elected in a special election taking his place, Democrats would need 4 Republican votes to kill Blanche's nomination.
Even if a Democrat won a special election it would at most be minimally worse for Republicans than a vacant seat or an incapacitated McConnell. Having a Democrat in that seat only really helps Democrats during votes where one or more Republicans are absent. Whether it's 52-47 or 52-48, Democrats still need 3 Republican votes in the senate to kill Republican legislation or nominees. A special election which would almost certainly be won by a Republican, would give Republicans back that 53rd vote for several months.
Worst case for Republicans with Special election, Democrats win but it has no real effect on Senate votes. However, if a Republican wins a special election , they get their 53rd vote back which is extremely significant.
A 53rd Republican in the Senate is an enormous advantage for Republicans (4 Republicans would need to join Democrats to kill legislation or nominees instead of the current 3 with McConnell not present), while a 48th Democrat effectively doesn't help Democrats at all (Democrats would still need 3 Republican votes to kill legislation or nominees - just like now).
Why is this so hard for so many to understand?
BTW, Andy Barr, the Republican candidate for the seat in Novembers general election is considered to have over a 99% likelihood of winning the seat. The chance of a Democrat winning a special election is only a tiny bit better. Before you say "but Kentucky has a Democratic Governor", Kentucky last elected a Democratic Senator in 1992. On the other hand, Kentucky has had only 2 Republican Governors (both for a single term) in the past 55 years. A Democrat winning the Governership in Kentucky is routine, having happened in 12 of the last 14 elections. Republicans have won 10 straight Senate elections.
https://www.racetothewh.com/senate/26#google_vignette