On Tuesday, the Republican Liberty Caucus of Colorado, former GOP congressman Tom Tancredo and Republican state Sen. Shawn Mitchell all came out in favor of Amendment 64, as supporters of the ballot initiative attempted to make their case to conservatives.

"The core value of the Republican Party is personal responsibility rather than collective prior restraint," the Republican Liberty Caucus of Colorado said in a statement." Personal responsibility means holding all individuals responsible for the actions they take rather than the words they use, the thoughts they think or the products they consume. Personal Responsibility means that a person who enjoys alcohol or marijuana without harming others is no criminal."

Joining members of the Republican Liberty Caucus at a press event in Denver, Tancredo described marijuana prohibition as a symptom of the "nanny-state." Last month, the former congressman compared marijuana prohibition to alcohol prohibition.

Mitchell also announced his support of marijuana legalization on Tuesday, saying it was "clear the War on Drugs isn’t working."

If approved by voters, the Regulate Marijuana Like Alcohol Act (Amendment 64) would allow for the limited possession and cultivation of cannabis by adults age 21 and over. It would also allow the state and local governments to enact regulations on the commercial production and distribution of marijuana, as well giving local governments the option to prohibit marijuana sales altogether.

Yes on 64 uploaded a video to YouTube on Tuesday that presented the "conservative case" for marijuana legalization. The video featured an old interview with economist Milton Friedman, where he criticized then-President Ronald Reagan for declaring a "war on drugs." The video also shows quotes from conservatives like Pat Robertson and William F. Buckley Jr.

Seventeen states and the District of Columbia have enacted laws to legalize medical marijuana. But Colorado would be the first state to legalize the drug for recreational use. A ballot initiative to legalize marijuana in California -- Proposition 19 -- was defeated in 2010.