If you had told me even five years ago that marijuana had the potential to be a major issue by the 2016 presidential elections, I'd have probably laughed and walked away. However, as the clock counts down to the next election -- now roughly 18 months away -- marijuana supporters and the American public are making it known that marijuana could be one of the defining issues that helps decide our next president.

America's rapidly changing opinion of marijuana

Public opinion surrounding marijuana has shifted dramatically over the past two decades. In 1995 there wasn't a single state where marijuana was legal on a recreational or medical basis, and public support for legalization stood around 25%.

Fast-forward to 2014 and just about every major poll taken suggests that a majority of Americans share a favorable view of marijuana. And, if these polls aren't evidence enough that things have changed, we now have four states that have legalized recreational, adult-use marijuana, and 23 states that have approved the use of medical marijuana.

But just because the American public is beginning to support some level of marijuana legalization or decriminalization, it doesn't mean that America's most-followed leaders are going to follow suit.

Hillary speaks her mind

Just three weeks ago Hillary Clinton declared her candidacy for the 2016 presidential election. Her declaration was something of a formality, but it meant the spotlight would officially be turned on Clinton's stances on a number of pressing issues -- including marijuana.

Although Clinton has largely ducked questions about marijuana in the weeks since declaring her bid to become the next president, she did state her opinions in a CNN town hall meeting in June 2014. When asked about the idea of legalizing marijuana nationally, Mrs. Clinton had this to say:

"On recreational [use], you know, states are the laboratories of democracy. We have at least two states that are experimenting with that right now. I want to wait and see what the evidence is."

And when asked about medical marijuana, Hillary had this to say,

"I don't think we've done enough research yet. Although I think for people who are in extreme medical conditions and have anecdotal evidence that it works, there should be availability under appropriate circumstances. But I do think we need more research, because we don't know how it interacts with other drugs. There's a lot we don't know."

Should Hillary Clinton's words shock you? Probably not, because in 2007, per CNN, Clinton came out decidedly against decriminalizing marijuana, but did note that research should be conducted into the drug to see if it has any benefits. It would appear that based on her 2014 town hall meeting answers she's begun to soften her stance on marijuana as public opinion of the drug continues to improve.

However, Clinton's words also bring up a number of obstacles that recreational and medical marijuana continue to face: the idea that marijuana's benefits and risks are still largely unknown since we have conflicting data from dozens of independent studies, and the fact that the federal government isn't going to rush into making a decision on marijuana until it has all the facts. In other words, marijuana might be an issue the American public wants tackled now, but Congress, President Obama, and presidential candidate Hillary Clinton all view it as an issue that can be put near the bottom of the pile in terms of issues to be dealt with.

There's also the issue of individual jurisdictions within marijuana-legal states continuing to ban the drug. If the federal government changed its tune on medical marijuana, or marijuana as a whole, individual jurisdictions within states could choose to simply ignore it and continue to implement their own laws. This "Swiss cheese" democracy could also cause marijuana's momentum to slow.

What's next for marijuana?

It's still too early to predict what side of the aisle other presidential candidates might fall on when it comes to marijuana, but I believe the one constant here is that marijuana is likely years, if not a decade or longer, away from being legalized medically or decriminalized on a federal level.

Lawmakers, by nature, will tend to be cautious with their words as election time approaches, meaning the answers we get on marijuana will likely vacillate perfectly between decriminalization and prohibition. What will matter most is that the next president, whoever he or she may be, continues to respect individual state laws currently governing marijuana. We can't say with any certainty whether the next administration will keep its hands off marijuana laws in individual states, but chances are probably better than 50-50, in my opinion, that the next administration will leave things as they are and use Colorado, Washington, Alaska, and Oregon, the four recreation-legal states, as models for what might happen if federal marijuana laws were relaxed.

What it means for your portfolio

Although we finally have the "experiments" in place that could validate marijuana as a beneficial drug for patients, or as a new source of taxable income for states and even the federal government, Washington's baby steps stance on marijuana and its potential reclassification once all the facts are in is bad news for the investor looking to profit from a potential surge in marijuana use.

At the moment there exist very, very few reputable marijuana companies that you can invest in. Most trade on the over-the-counter exchanges and are losing money. Some, comically, weren't even involved in the marijuana business until the last year or two.

Investors' only apparent shot at making money off marijuana is GW Pharmaceuticals (NASDAQ:GWPH), a drug developer utilizing cannabinoids from the cannabis plant to effect positive biologic change. GW Pharmaceuticals' pipeline of six cannabinoid-based drugs has yielded positive data for rare forms of epilepsy via Epidiolex, but it's also featured the failure of Sativex in the first of three phase 3 studies as a treatment for cancer pain. Although this is probably investors' best shot at investing in marijuana stocks, it's still a high-risk play. With losses expected throughout the remainder of the decade, and marijuana policy looking as if it'll remain unchanged too, you might be better served keeping your money as far away from GW Pharmaceuticals' stock as possible.