It could be 90% in favour of rejoining, but it wouldn't make much of a difference. The EU would need to see strong, long term cross-party support in Westminster before they'd consider it. The EU know that otherwise the issue is just going to keep re-emerging in UK politics so long as the Tories are ideologically opposed to the EU. I think the best chance the UK has is if the modern Tory party stopped being relevant electorally, because their membership's views aren't likely to change, and everyone in the EU institutions hates them for the damage their governments have done over the last 7 years.