I suspect the current setup will unravel in 2022 leaving options wide open for new alliances.
With one exception---Kibaki's first victory, which was after a very length beating from Moi----"tribe" is what matters to Kenya when it comes to voting, and one thing tha won't unravel in 2022 is the "our man" mentality.
I mention corruption and ethnic cleansing just to show that GEMA does not even have to rely solely on tribe to reject him, even if that is a primary reason. In other words, they can even reject him with respectable reasons.
Would corruption really be an issue for GEMA? There is definitely residual bitterness in relation to the ethnic cleansing, but it seems to have been decided that money and power are more important and that certain things will have to be swallowed.
The real question is this: If they reject Ruto, to whom will they turn? I see no reason to believe that they will be welcomed elsewhere with open arms.