The incumbency advantage is reduced by the presence of devolution. He is no longer the centre of largesse as governors also dish it out. CORD's main problem is the media. They have to either own their own TV or convert one of the major ones before 2017. Jubilee is able to arm twist the entire media to blackout CORD as we saw with saba saba and to drown them as we saw with the "Accept and Move On".
It is a major challenge. Raila can sort it out by drawing on his international contacts to help him start a private TV station with the capacity for satellite broadcast in event the local transmitters are disabled. He can borrow leaf from the Serbian Opposition to Milosevic which suffered in a blitz of nationalist fervour against one of the precursors to the ICC. In that case the US came to their aid by using their satellites to beam signals all over Serbia and thus gave the Serbs an alternative view.
It's too early to do tribal maths but i'd say Uhuru enjoys advantage of incumbency (and of course the disadvantage of having to deliver promises and get blamed for everything wrong) but CORD have 3 of the big 5 in their corner.