Most countries immunize declared candidates for parliaments or the presidency, because it's a basic premise of democracy. If the population, by direct referendum, believes this person should be in government, whatever forces that are doing the prosecuting are a minority.

Makes sense to have some minor flexibility in this standard, so people aren't continually running for elections in order to stay out of prison. But if (for example) a criminal like K. Fujimori is running for president of Peru, she is obviously a serious candidate and shouldn't be legally threatened.