I am wondering whether it is possible to limit the possibility to vote in a poll to certain groups. Should that not be the case, I figure it would be easy to add that functionality, would it not?
Sure, create a category, give only that group permission, create a poll in that category 
3 Likes
I specifically asked about the right to vote instead of access, because some processes should be transparent but taking part in them should be limited. Sorry for not clarifying earlier.
Do reply permissions include those for votes? Then disabling those in the categories in question is not nice, but it could work.
2 Likes
Just to tie this one off, this has been possible for some time. 
You can choose which groups can participate in each poll using the Limit voting to these groups option in the advanced section:
Can you vote in this poll?
- Yes
- No…
0 voters