Surely it's been a difficult decidion, at least since the rise of Blair and Blairism. Luckily, until we are finally out of the EU, there is a party one can vote for both in good conscience, and knowing they're most unlikely to form a government.
Reality dictates one must accept a right wing government next anyway, and until the left drops the idea of controlling and monitoring free citizens by trying to impose compulsory papers/id cards they will remain difficult to trust.
In reality there will be no party, and I fear, no individual, worthy of supporting. But when they bring in compulsory proof of id in order to vote the % voting will drop so much, you dropping out too won't be noticed. We'll have all gone to hell in a handbasket and even Brexit won't be able to compensate.