Not that big of a deal, I’m thinking. Let’s imagine that Reince Priebus was running for POTUS and got the nomination. Seems fairly reasonable to me that he would have resigned as GOP chair to do the full time candidate thing for the general election. They run things a little different in Europe, but this is not as important as it would be in a Parliamentary system like they have in Britain.
I agree with your overall point, not that big a deal.
I will reference you to this other story, where it says temporarily steps down. That causes me to think we’re dealing with something different than the examples you gave.
http://www.freerepublic.com/focus/news/3546938/posts?page=24#24