Presidential hopeful Gary Johnson knows his support for legalizing marijuana will be used against him by opponents of his quest for the GOP presidential nomination. The libertarian-leaning former Governor of New Mexico will announce his candidacy for the Republican presidential nomination on April 21st in New Hampshire.

Before delivering the keynote speech at the High Times Cannabis Cup in Denver, Colorado, Johnson told Fox News he is prepared to be attacked on the pot issue.

"I just want you to know I caught a lot of flack on this as governor, and I more than survived," Johnson said. "I've debated this issue more than any politician on the planet. And this is an issue that under the light of day does really well."

Johnson served as Governor of New Mexico from 1996 until 2002. He began advocating marijuana legalization during his second term when he realized the War on Drugs was inordinately consuming state and local resources.

"I wanted to crack down on drinking and driving in New Mexico," he said. "And I had conversations with law enforcement, the courts and the prisons. Basically all three said, 'We are so busy, our dockets are so full that if you want to have this kind of initiative you better give us some more money, more resources'"

Johnson says that half of the time and resources of state and local law enforcement, courts and prisons was being spent on drug related crime. To him it looked like just another failed government policy, throwing more and more money at a problem with little to show for it.

"People who have sold small amounts of drugs, which is actually still the majority of those behind bars...they've been caught and they've done it numerous times and been caught and now they're there on mandatory sentencing."

Johnson views that as government waste, which he believes conservatives should be against. "Why is it for Republicans that government messes up when it comes to all sorts of regulation of the economy, but they have it right when it comes to...drugs? The government has completely messed this up! From a conservative standpoint, A through Z, how can you not support the notion of a rational drug policy?"

When asked if he smoked marijuana in his youth, and if he inhaled, the former Governor answers unhesitatingly, "Yes I did, yeah I did. I have a very public record."

In fact Johnson has previously admitted using marijuana for medical purposes between 2005 and 2008. He says a caregiver gave it to him for pain he suffered as a result of a paragliding accident in which he broke several bones including one of his vertebrae. Medical marijuana was not legalized in New Mexico until 2007.

"I haven't had a drink of alcohol in 24 years. But having smoked marijuana and having drunk alcohol... there's a big difference between the two, and the difference is that marijuana is a lot safer than alcohol. It just doesn't have the negative behavioral consequences that alcohol does. And it will never be legal to smoke pot and become impaired and do harm to others. It'll never be legal to smoke pot and commit crime, just like alcohol."

The presidential hopeful also sees the failure of the war on drugs as the cause of most of the violence on America's southern border.

"You want to address this, legalize marijuana. Start with legalizing marijuana. Arguably 75 percent of the violence along the border with Mexico goes away. Don't you know when you hear about a killing along the border, the killing of a U.S. border patrol agent, it's drug related."

Johnson knows his position on this issue will overshadow his stands on others during the weeks ahead. "In this endeavor I'm going to be labeled the pot candidate. It's just, it's the reality. But I can't avoid it. I can't not talk about it, because then I'm avoiding it. But the reality is also, if I hang around it's going to shift. You can't be just talking about marijuana, which I'm not!"

And he seems to sincerely believe when it comes to legalizing marijuana, he is on the forefront of an issue that is at the tipping point.

"This is an issue when 46 percent of Americans support legalizing marijuana. Statistically, zero percent of politicians support legalizing marijuana. Before alcohol prohibition was repealed, not one single politician supported that notion. Immediately after it was repealed you could not find a politician that was not in support of that. I think this is a similar situation. This is one that is going to completely leave the politicians in the dust, totally."