We simply convince everyone with an IQ of lower than, say, 85, to voluntarily walk into a government run booth. There is a bright flash, and a pile of ashes. It's called eugenics.
Democrats and their various voting blocks will sorta take it in the shorts, but I'm sure they will understand, since it's for the Common Good. We could tag them as "Anti-Gaia".
We could throw in SAT scores, and ACT scores along with ASVAB, sort of a combination deal, and convince all the college students that the booth is a "safe space". Anyone that stupid would be a prime candidate...
The BBC Dr. Who spin off “Torchwood” broached that topic. The show message was how horrible that decision was but I thought it was making the best of a list of horrible choices.