By now people know defectors are a meaningless yardstick for popularity. They wont change the tribal arithmetic unless they are one of the big fishes.
Defections used to mean a lot immediately after Independence and after the repeal of Section 2A of the constitution in December 1991.
It has slowly lost value as Tumbocracy shaped up to become an ideology.
As of now Kenya is fully tribal. Those who can mobilize their tribes can probably command 70% of the votes. Note that whether there is a civil war (the requisite historical condition for shaping a modern Nation), tribe as a unit is endangered. It will die not because of slogans and appeals (Uwiyano or some such NGO thing) but because the middle class (which was a US and later European thing after WW2)is growing and expanding to and within Africa, Kenya included.
Policies and votes will be determined by how they will affect the family pocket not the tribe.
As of now Uhuru re-election is not even fifty-fifty. If you held elections today he would lose and try a Kibaki(2007). I see the defections and reversing accusations about hacking etc as part o0f the preparations for a possible Kibaki.