A single vote by 350,000,000 people with 250 bytes of data per vote would use over 87.5GB on the blockchain. That's just in a really simple case but usually a ballot has like 50 things on it.
This is a time-based problem. Meaning that gigabytes are important in 2018. In 2028 terabytes might be important while megabytes are seen like gigabytes today. And in 2038, gigabytes might be regarded as kilobytes today: trivial.