forcing portal users to rank ideas

portal users can obviously vote on any idea but there needs to be a feature that forces them to rank/prioritize the ideas they have voted on so they get to play their own product manager and make the tough calls on which of their ideas is most important to them vs least. a dropdown based priority field (needed by) doesn't protect against all ideas being marked as "urgent" so such a capability is quite valuable.

for instance, we could have

idea 1 with 5 votes
idea 2 with 5 votes

>> scenario 1 (votes only) : both will be treated the same
>> scenario 2 (votes + rank) : if 5 customers have idea 1 as their number #1 priority where idea 2 as their #10, i would want to (as PM) - give more weight to idea 1.