Re: Dodgy behavior by Vote Leave?
There are various ways that can work. In Switzerland, votes on two different projects are typically represented as:
1) Do you want project A?
2) Do you want project B?
3) In case both A and B are accepted, which do you prefer?
It's typically better to ask all questions at once, because it avoids forcing people to vote against their own wishes for strategical reasons.
For instance, in your proposal, people might prefer no deal to May's deal, but worry that no deal cannot get the majority in the second vote, so end up voting for May's deal in the first one. People who want to remain might vote for no deal in the first vote, hoping that it will not get a majority in the second, etc.
Then again, no multi-ways voting system is perfect; there are various paradoxes.