Americans have drastically changed their opinion on marijuana legalization over the past few decades. So it would seem obvious that politicians' opinions on marijuana would change as well. And while the vast majority of politicians currently in office, at least at the federal level, continue to fight against legalization, some of them have evolved on the issue. Although some of them have gone in the wrong direction as well.

Here are the six most prominent American politicians who changed their opinions on marijuana.

6. Paul Ryan

Before Ryan served as Speaker of the House, he was chosen as Mitt Romney's running mate in the 2012 presidential election. While on the campaign trail, Ryan said in an interview that he believed states should be allowed to decide their own policies on marijuana. For a Republican politician, this was a surprisingly progressive take...and one that contradicted Romney's platform. Just days later, Ryan re-affirmed his position that marijuana should remain illegal in all instances and he's continued those positions to this day.

5. Bill Clinton

After he famously told the American people that he didn't inhale, Clinton supported anti-marijuana policies while president. He even explored the possibility of punishing doctors for even discussing medical marijuana with patients. In 2014, he changed his opinion, saying he believed that states should decide their own opinions on marijuana and admitting that their was "a lot of evidence" about the medicinal benefits. 

4. Michael Bloomberg

Before serving as mayor of New York City, Bloomberg was asked about whether he ever used marijuana. He responded, "You bet I did. And I enjoyed it." Sounds like a guy who would support marijuana legalization, right? Well, not exactly. Bloomberg has strongly opposed any efforts to legalize marijuana since becoming an elected politician. I guess he just doesn't want people to experience the same joys he did.

3. Hillary Clinton

Like her husband, Hillary's done a complete 180 on marijuana legalization. While running for the Democratic presidential nomination in 2008, Clinton said she opposed marijuana legalization. But during her 2016 campaign, she said she approved re-classifying marijuana as a Schedule II drug and protecting states that want to legalize it. 

2. Donald Trump

Like many issues, Donald Trump's younger self had a much more liberal stance when it came to marijuana and drug legalization in general. In 1990, Trump said he supported legalizing all drugs, saying that doing so would rob cartels of their profits and lead to victory in the War on Drugs. Fast forward to his 2016 presidential campaign, and Trump told Sean Hannity that Colorado legalizing marijuana was "bad" and he "felt very strongly about that." And his appointment of known anti-marijuana advocate Jeff Sessions as Attorney General is about as far away from someone who would want to legalize all drugs as possible.

1. Barack Obama

Former President Barack Obama is the rare politician who underwent a double flip-flop on marijuana during his career. While running for Senate in 2004, Obama told a group of college students that he supported decriminalizing marijuana. Less than four years later, he opposed marijuana legalization in his 2008 presidential platform, and his Justice Department cracked down harshly on marijuana. Then, near the end of his presidency, Obama softened his position on marijuana and became an advocate for lowering penalties on marijuana possession and acknowledged possible medical benefits. If only he had taken that position sooner.