Less than 10% of prisoners are in private prisons - getting rid of private prisons would have little impact on support for the drug war.

https://en.wikipedia.org/wiki/Private_prison

Which isn't to say that public sector unions and companies that supply material to prisons, or built prisons don't all support polices that incarcerate more and more people. (For example, the CA prison worker union spends more on political lobbying than all other labor unions in CA.) https://en.wikipedia.org/wiki/California_Correctional_Peace_...

Said it yourself in the second part.

>>"The American prison system is massive. So massive that its estimated turnover of $74 billion eclipses the GDP of 133 nations." https://smartasset.com/mortgage/the-economics-of-the-america...

Alternatively you could have completely open interests in public correctional officers unions. Over 90% of prisons in the US are public and their employees are at least as highly motivated as any investor to lobby for more punitive laws and they can vote.