Colin Campbell, Business Insider

Polls show the vast majority of the public - around 86%, according to a January 2014 CBS poll - supports medical marijuana legalization and a slight majority favors outright legalization for recreational use. However, though a growing number of states are passing laws to relax restrictions on marijuana, many of the likely leading contenders in the 2016 presidential elections have been slow to jump on the bandwagon. Despite this reticence, some marijuana advocates are hoping the issue takes center stage when voters pick a successor to President Barack Obama.

Hillary Clinton, the undisputed Democratic front-runner, said in June she supports the medical use of the drug for "extreme medical conditions." Beyond that, Clinton said she has a "wait and see" approach and wants to watch how laws legalizing recreational use in Colorado and Washington work before fully determining her position on that issue. Other Democrats thought to have national ambitions - including Vice President Joe Biden, Maryland Gov. Martin O'Malley, and New York Gov. Andrew Cuomo - have been similarly cautious despite being outspoken progressives on other social issues like abortion rights, gun control, and same-sex marriage.

Time magazine reported in February that Biden "is essentially unchanged from a 2010 interview with ABC News in which he called marijuana a 'gateway drug.'" O'Malley threatened to veto medical marijuana legislation in 2012 only to sign a bill - graded a "D" by Americans for Safe Access - in 2014. Cuomo signed new legislation Monday that made the Empire State the 23rd to legalize medical marijuana. But the bill was so restrictive, including limiting marijuana production in the state to just five manufacturers, that many advocates were left frustrated. ASA rated New York's law an "F+."

"I said from the very beginning when we started that we were going to make sure that New York had the tightest most regulated system in the country because if we didn't, Andrew Cuomo wasn't going to put his signature on it," State Senator Diane Savino, a lead sponsor of the bill, told Business Insider Wednesday.

Packets of marijuana on the first day of legal recreational pot sales in Seattle, Washington.

Multiple Democratic observers told Business Insider they have been left dumbfounded by the positions politicians in their party are taking on marijuana.

"I am perplexed as to why Cuomo wouldn't embrace something more expansive," one national strategist told Business Insider, requesting anonymity in order to speak candidly about party leaders. "I have not really fully comprehended why other governors are not embracing this."

Republicans have often been even more wary than Democrats of increasing any use of the drug. Across the Hudson River, GOP Gov. Chris Christie, who is weighing his own run for the White House, claimed in June that medical marijuana is "a front for legalization" efforts in New Jersey. Christie is accused of "sabotaging" his own state's medical marijuana program, which was signed into law before he took office in 2010.

Political operatives and strategists cited several reasons White House hopefuls might be slow to get behind growing support for marijuana legalization.

One Republican pollster who spoke to Business Insider about the issue suggested politicians are walking a "tightrope" when it comes to marijuana - trying to balance increasing support for legalization with concerns backing looser laws will hurt their standing with other voters.

"It's a very polarizing issue when it comes down to it. Because when you're a politician you don't want to be seen as legalizing marijuana," the pollster said. "They have to do the tightrope on this thing because they don't want to be seen as someone who's too liberal on the legalization."

The national Democratic strategist suggested Baby Boomer politicians may be holding views on marijuana from that older generation. However, the operative suggested they need to recognize the "dramatic shift" that has occurred since then.

"It's undergone this dramatic shift even in just the last few years in public opinion polls and I think it demonstrates just a cultural shift in that people aren't captive to the stereotype of marijuana from the dormitory wars of the 1960s. It's not a counterculture symbol. It's a proven medical benefit to a whole lot of suffering families," he argued.

Yet another national strategist suggested the law enforcement backgrounds of many elected officials creates some hesitation around the pot issue. Indeed, Cuomo is a former state attorney general, O'Malley is a former assistant state attorney, and Christie was a U.S. attorney.

O'Malley referenced his prosecutorial experience to explain his evolution on drug policy before signing a decriminalization bill in April.

"As a young prosecutor, I once thought that decriminalizing the possession of marijuana might undermine the Public Will necessary to combat drug violence and improve public safety. I now think that decriminalizing possession of marijuana is an acknowledgment of the low priority that our courts, our prosecutors, our police, and the vast majority of citizens already attach to this transgression of public order and public health," O'Malley said at the time.

Allen St. Pierre, the executive director of NORML, a nonprofit lobbying organization working to legalize marijuana, told Business Insider he could only think of a handful of governors over the past two decades who have seen marijuana as something they shouldn't inherently approach as an adversary.

"It's a pretty rare thing and this has been vexing because ... the polling numbers are pretty stark," St. Pierre said.

But not every presidential hopeful has been slow to embrace marijuana reform. Two Republicans looking at running in 2016 - Texas Gov. Rick Perry and U.S. Sen. Rand Paul (R-Kentucky) - have been willing to speak out in favor of less restrictive penalties.

"You don't want to ruin a kid's life for having a joint," Perry said in March at the South by Southwest conference in Austin. ("Does second-hand count?" Perry replied when asked if he ever smoked the drug. "Because I think there's still some left in there where Snoop [Dogg] was.")

In addition to working with Democrats to soften penalties, Paul supported a Senate effort in June to block the Justice Department from going after medical marijuana users in states where it's legal. This has led some Republicans to predict their party will get out ahead of Democrats on the marijuana reform issue.

"You're going to see Republican candidates at the national and state level taking that up as well," GOP strategist Rick Wilson said of the push for marijuana decriminalization "We're out of the 'Reefer Madness' days of the Republican Party. We're out of the 'Just Say No' days."

Sill, several other leading Republicans have nevertheless been vague or outright hostile on marijuana reform, including Sen. Ted Cruz (R-Texas), who criticized Obama for not cracking down on users in Colorado. However, advocates like St. Pierre are nevertheless hoping the 2016 election cycle will be their year.

"A serious debate will be in play," St. Pierre said of 2016, citing a California ballot initiative for recreational use as well. "Whether that will be someone like Mr. Paul, who will run on a libertarian plank, or Martin O'Malley, who may have to run to the left of Mrs. Clinton. ... I think 2016 will be the penultimate year for medical marijuana reform."