Kalonzo Musyoka failed to show up and take oath on 30th January 2018. This wasn't pleasing to the NASA coalition supporters who were astonished to see ODM leader Raila Odinga take the oath as the people's president in absence of the Deputy people's president.
Kalonzo has in many occasions portrayed that he is not interested in taking the oath and at one point even said that the oath will be unconstitutional.
To start with, Kalonzo is more keen on his 2022 presidential bid. Having ran for presidency during the 2007 polls and as a running mate in the 2013 polls, the Wiper leader wants nothing less than to be a presidential candidate come 2022. Thus, taking an 'unconstitutional' oath will hinder his chances of being in the ballot in the next General Election.
Secondly, the former Vice President has to fight hard to avoid being a running mate again. For instance, in the current political set-up in the opposition coalition, Raila Odinga still sits in the top seat and this maybe very difficult to give chance for anyone else to run for presidency. Therefore, by not taking oath, Kalonzo has differentiated himself from the public view that he is just below Raila, who is considered Kenya's opposition leader.
Lastly, by not taking oath, Kalonzo is placing his political career in a lucky situation. Preferably, he would consider being a running mate yes, but on the winning side. Let's say, there exists chances of DP Ruto picingk him for a running mate, who knows! In such a situation, Kalonzo had and has to play safe to avoid being a political loser in the near future.