I understand how appealing this sounds. But as someone who's studied both voting and e-cash protocols before blockchain was ever around, I'll say this: no one ever said the problem with online voting is "double spending" aka double voting. That is not an actual problem.
The problems with online voting, with or without blockchain, are 1/ securing the user endpoint, and 2/ providing voter-understandable evidence that their vote was correctly recorded.
Blockchain solves neither of these. Where voting is concerned, blockchain solves minor problems that are much more easily solved via much less onerous means. See benlog.com/2017/12/28/blo…
The hard problems of online voting, the ones we don't know how to solve? Blockchain does nothing to address them.
