It focuses our attention, but that often quickly triggers mechanisms to protect our partisan opinion.
When shown an election ad that attacks the party that the person intends to vote for, or that they belong to or campaign for, ego protection mechanisms are activated in people's cognitive processes to deconstruct the argument presented. This focuses our attention and triggers a stronger cognitive process, but there is not necessarily a ripple effect. If the ego protection mechanism works, it will instead lead us to establish our partisan position more firmly and protect us from the potentially persuasive effect of the advertising.
Of course, I have not studied the cases you mentioned so I could not comment on them. In the case in Africa that you mentioned, we could assume that the citizens who support the party being attacked will use an argument, more or less consciously, to protect their political convictions concerning the party under attack.