(CNN) Beto O'Rourke's campaign on Thursday unveiled his proposal to legalize and tax marijuana, release and expunge the records of those convicted of marijuana possession and help businesses that sell marijuana use banks.

The plan puts down on paper a proposal that has been at the core of the former Texas congressman and 2020 Democratic presidential contender's entire political career.

In 2011 he co-wrote a book arguing for the legalization of marijuana, saying it was a crucial step to reduce violence in Mexico. He then entered national politics by ousting Democratic Rep. Silvestre Reyes in a 2012 primary with a campaign built on challenging Reyes' opposition to marijuana legalization.

As a presidential candidate, O'Rourke has framed the issue as a matter of racial injustice, pointing out in Iowa in March that those arrested on marijuana-related charges are "browner and blacker than most of America."

His plan aims to regulate marijuana in ways much more similar to alcohol: requiring IDs to buy it, focusing on deterring driving under the influence and limiting its use in public spaces.

Read More