Resisting against votes

In France when people say No to European constitution the Prime Minster resign and appointed a new prime minister .
why? because people say no to an important referendum that wasn’t so related to government .
but Prime Minster resigned (dismiss) because who are in power found that best reference for understanding what people think is votes that they give not demonstration that government set them up.
but in Iran in 1998 when 70% of people chose reformist president khatami conservatives who have real power not even gave up though they resist against people decision and with appointing extremists and rival of reformist in important place of regime try make problem for reformists and people.