I do not believe they do. They only need to appoint a president after the election, but it is usual for parties to announce who their appointee will be before an election. Though, not having a list or presidential nominee prior to an election would certainly cost such a party dearly where public votes are concerned. I am sure you are aware that, other than the USA for instance, our system means we vote for a party who, after and if they win, appoint the president.