Will Texas decriminalize pot? Why conservatives are getting behind the legalization movement.

A panel in Texas's House of Representatives voted to approve a measure that would decriminalize buying and selling marijuana in the state.

In a decision that surprised even legalization advocates, a Texas legislative committee approved a bill Wednesday that would decriminalize buying and selling marijuana in the state.

While the bill has almost no chance of clearing the necessary legislative hurdles to become law in the deep-red state, it signals a surprising development in the legalization movement: shifting attitudes toward cannabis by conservatives.

"Marijuana policy reform continues to make unprecedented progress this session," Phillip Martin of the liberal group Progress Texas tweeted just after the vote.

Known as House Bill 2165, the proposal would make Texas the fourth state to legalize marijuana for recreational use. Currently, Colorado, Washington State, Alaska, and Oregon have legalized pot, along with Washington, D.C.

The bill passed the Texas House Criminal Jurisprudence Committee 5-2, thanks to two Republicans, including David Simpson, who joined the panel's three Democrats in approving the measure.

State Rep. Simpson, a Tea Party Republican, represents the changing attitudes toward cannabis by conservatives. 

"The time has come for a thoughtful discussion of the prudence of the prohibition approach to drug abuse, the impact of prohibition enforcement on constitutionally protected liberties and the responsibilities that individuals must take for their own actions," Simpson wrote last month in an op-ed for the Texas Tribune, titled "The Christian case for drug law reform."

"I don't believe that when God made marijuana he made a mistake that government needs to fix," wrote Simpson.

Nationally, a slim majority – some 51 percent of Americans, according to a 2014 Gallup poll – now supports legalization. But a recent Pew poll found nearly two-thirds of Republican millennials favor marijuana legalization.

Some 63 percent of GOP millennials (those born between 1981 and 1996, according to Pew's metrics) said marijuana should be made legal, while 35 percent say it should be illegal, according to Pew's February 2014 survey.

The survey shows Republican millennials are far more supportive of legalizing pot than their older counterparts – only 38 percent of GOP Boomers say it should be legal. But Democratic millennials are the most supportive, with 78 percent favoring legalization.

Why are more Americans – and more conservatives – beginning to support legalization?

Many Americans view marijuana as less harmful than alcohol, and most Americans think those convicted of possessing small amounts of marijuana should not have to serve jail time, according to Pew's report.

And a strong libertarian streak staunchly opposed to government intervention runs through the Republican mindset, making them odd bedfellows with typically liberal legalization advocates.

As Taylor Bickford, a spokesperson for the Campaign to Regulate Marijuana Like Alcohol in Alaska, told Vox News when Alaska voted to legalize marijuana, "People here generally want to be left alone and really don't think the government is the solution to their problems."

Two state representatives, Republicans Matt Shaheen and Jeff Leach, both of Plano, voted against the measure.

"If we reduce the fine for speeding, there's going to be more speeding and onward and onward," State Rep. Shaheen told KVUE, ABC's Austin affiliate. "This is reducing the penalty for the use of marijuana. What that means is it's going to drive up the use of marijuana, including children, and that's a huge concern."