The Bible does not forbid voting on a referendum regarding a law. The Bible does not forbid voting for government leaders. But that does not mean that God does not care who or what we vote for. As best we can, we should use a trained conscience in understanding which laws or approaches are wisest. Power and authority should be used wisely.
Most issues are complex.
A law that emphasizes one type of justice may unwittingly be unjust in other ways. A candidate may be right on one issue but wrong on others. Christians might therefore make opposing decisions on the same issue, but they must accept one another as members of the same family of faith. We must remember that truth cannot be determined by majority vote. Voting is simply a temporary system of administrative convenience.