Not possible to do in any serious scale in Nairobi
Agents from all parties are hawk eyed.
In Nairobi there is confusion because on primary has like 30 streams - but still they are so many agents/observers - like 10 to 20 people - each MCA has their agent, gov, name them....so many people watching every action.
Rigging that has happened post Maina Kiai - has happened chieftly in NORTH EASTERN KENYA.
With Maina Kia rulling - results from polling station are final - cannot be altered or corrected - just tallying them up.
Rigging will happen in areas where
1) Party enjoys say 97 percent of support - this time it's Kalejinland and LuoLand - hapo all agents, observers and polling clerk can agree to assist their candidate. Normally what happens - MCA - to Governor votes - are very clean - they are done and everyone who wont be tired by midnight then assemble to rig the presidential votes last - and hapo big time collusion happen. I believe Uhuru rigged in some of such areas in Mt kenya...the variance btw presidential and other votes is dead give way. Raila has been rigging this way since 1992! This kind of rigging balance out -and results in very high almost unrealistic turn out in such areas.
2) Remote areas like NEP - with polling station - located deep - no agents - no observers - NIS can sit under a tree and cook figures. There has been massive rigging in NEP in both 2013 and 2017...but thankfully their votes are so few. Mandera in 2013 was massively rigged in favour of URP by Somalis.
In the future we need to fix both - by I guess installing CCTV cameras?
If Kenyan elections are compromised they are not done By IEBC top officials or at Bomas Tallying Center.
Nor is it done during counting , by then Cameras are rolling and agents alert.
The elections are compromised after voter identification and during hamding over of ballot papers to the voters. In Nairobi thats how Kidero and Sonko played in 2017 Based on how the electral officers were corrupted and the stations . The voters were being given 2 to 3 Governor ballot papers to mark and slot in the ballots . One reason you saw the Governors polling more than the Presidential candidates.
The electral officers could identify Sonko and Kideros voters by a coded signal or simply by features .
Sonko knew he had won by midday .