Hi Michael,
I'm actually kind of surprised you don't know who oppose it, or this maybe more of a rhetorical question?
Adults who would (as a general rule, not all) oppose legalization of marijuana:
* drug rehab centers, the owners and employees of such facilities (and even further extending to those who service those facilities such as suppliers of medical supplies and equipment, food service, etc)
* City, state and federal police officers who are employed by or have budgets tied directly to the arrest, conviction and encarceration of those who oppose the law
* (this one is hard to post without offending or at least violating the TOS)..."Conservatives" - this is a large group and while all those who consider themselves "conservative" would not necessarily vote to prevent legalization, the group still includes a large percentage of people who would vote against legalization when you consider "Conservatives" include most "Christians". And even tho not all Christians are "Conservative" and not all Christians would vote against legalization, it's still a large percentage of people when you consider the ones who would.
determining what percentage of that group which would vote against legalization would be difficult and would most likley cause problems on a "non-political/non-religious" forum.
so, I have to believe that your question is actually fairly short-sighted at least, possibly since you likely do not "fraternize" with people who fall into these categories?