Oregon is within 800 votes of winning GMO labeling at the ballot this year, and the measure is currently in a recount.
Ballot measure 92 GMO labeling results as of Dec 8 (95% of est. votes counted):
Yes 752,720 50.0%
No 753,537 50.0%
Big food companies like Monsanto, Dow and others threw a fit over the costs of labeling produce and products in one state only, but clearly other states would jump in demanding labeling if it passes in Oregon. Eventually, it would be the companies' choice to label only for sale in public interest states rather than in every state.
Oregon is 100% vote by mail, so ballots are verified by signatures. Voters have the option to verify their ballot after the election if their signature caused them to be rejected. This year, some voters have sued over this issue.
Coming this close to wining GMO labeling despite big businesses' record-shattering spending to mislead voters makes me think that the next ballot measure would likely win. Gotta love states that allow citizens to write and pass their own laws!