Board Thread:The Quarters - Q & A/@comment-86.19.126.249-20150711225956/@comment-24150802-20150717104620

One other option is for all of the active party members to leave that party and form their own. It can have the same name as the original party, if desired. If you want to do that, the person who will be the new leader should collect the User IDs of all active members before they leave.

To be honest, this is a better process than having the leader changed against their will. It is still their party, even though they aren't active at the moment.