SELECTing percentage and count of votes
It took me a while to realize that you must be considering a poll to be a single question (posted on a web page) that allows people to pick from a series of options for that single question.

Some things to consider:


[options] Consider reversing the index field order. It would seem probable that you will want to query up the options for a poll without specifying the option_id.
[questions] There appears to be no real point to indexing the deleted bit. When pulling questions up for a poll you can certainly exclude those that are deleted without needing an index.
[votes] I'm guessing that 'nick' is the login name of the user choosing an option from a single question poll?
Look at an explain to see if MySQL has optimized your sub-query into a single lookup. If not, do your own explicit query or consider using group by modifiers to do a rollup when you pull up poll stats. Then, in either case, as you load records for a poll (as you'll have some code for web display purposes) do the percentage calculation as you generate the output table. 


Finally, it is customary to "select count(*) from tab" when you don't care about the columns involved.