Not a historian, but from what history I know, it generally depends on the momentum of the person who was assassinated.

If the assassinee is both a) popular and b) not a force in the status quo, then I would say that generally assassination halts their platform.

If the assassinee is popular, and at work in the status quo, it only serves to make their platform more visible and therefore generally stronger.

One example I can think of of the first situation are the Roman Gracchi, who were populists during the late Roman republic. Assassination of two successive ‘Brothers of the People’ led to a complete route of their platform - the Lex Agraria.

There are many examples of the second situation - MLK jr. is an easy one. The platform of MLK jr. had already come to be accepted in the nation’s consciousness as right - it is only the logical conclusion of the cessation of legal slavery some 100 years prior. Therefore, when he was assassinated, it only served to justify the directive of the nation.

I’m certainly open to examples exploring exceptions to the two cases provided, as well. I think it’s an interesting topic.