First off because "IQ tests" don't test for brainworms. There's plenty of people who possess the mental capacity to pass a test like that, but who use that brainpower to come up with creative ways to defend wrong ideas rather than thinking critically. This is a large part of why IQ tests are meaningless, because even if they were capable of accurately assessing raw brainpower, they're certainly not capable of assessing how you choose to use that brainpower.

If you make a test that does test for brainworms then you have the question of who or what body decides what's a brainworm, and at that point you might as well just give that body dictatorial control. There's no possible way to do that in a remotely objective fashion, the body could easily just say, "Capitalism is obviously right so anyone who doesn't agree with it should be barred from voting." Or, if it were me, I might decide that anyone who thinks that people having low IQs is the problem with our political systems is, themself, obviously unqualified.

Really, it's not that different from the Catholic Church gathering together a bunch of highly educated scholars behind closed doors to debate what they thought made sense and then trying to enforce that on everyone. At least way back then, they had the justification that most of the population was fully illiterate.

I'm going to address only the last part: what is the value of having stupid people vote.

The value in allowing stupid people to vote is that your opposition can't change the definition of "stupid" to include only you and your friends.

The law is a blunt instrument. If we enshrine in law the power for Congress to deprive people of their vote, we have agreed that depriving people "for the right reasons" is justification for doing so, and now the question simply becomes "can you convince people this is a good reason to deprive people of their ability to vote".

We already have this with Felons. They are a miniscule percent of the population though, so it cannot be abused to win an election. It's bad enough the precedent kind of already exists. Expanding it would be self destructive

EDIT: Because it's been brought up, felons who cannot vote make up 1.1% of the US population.

IQ tests are too problematic. Let's go old school and you need to be a 18+ male land owner to vote. /s

Democracy but you gotta pass an IQ test threshold to vote/run?

Dude, they already tried that in US. Learn some history.

The problem with intelligence requirements is two-fold.

First, intelligence is difficult to quantify. I often hear that IQ tests are unreliable or only test for certain areas of what could be called intelligence.

Second, such requirements would instantly become politicized and designed to prevent certain groups from being politically active. This exact thing happened after the US civil war when literacy tests were required and designed specifically to keep black people from being able to vote.

Additionally, I just don’t know that intelligence is the quality that matters most. A selfish smart person is just going to be good at benefitting themself politically at the expense of others. The focus should be on getting more people politically active who will use their political power to benefit others beyond themselves. Of course, that’s probably even more difficult to test for than intelligence.

I think the better way to do it is to have a test which doesn't test for intelligence (although I agree that it basically does test for intelligence but not explicitly) but for understanding of the topic at hand.

It's a simple test, it's just one question, "what, if elected, would this person do?" You must be able to identify at least one actual policy of the politician you're voting for. Trump told everyone who he was, and what he would do, and they still voted for him and then acted all surprised. Because they're total exposure to his policies was whatever they read on Facebook which was actually not what he said.

IQ is inherently racist

Do yourself a favor and read the book 'Starship Troopers.'

The author has a ball playing with political ideas. His take is that after WW3 [a limited nuclear was, not an all out holocaust] angry veterans returned home and saw anarchy. They united and cleaned up the baddies, then enshrined the idea that only veterans would be allowed to vote. Centuries later, anyone, no matter how physically weak can join the military and do a term of service and get full citizenship. It's explicitly stated that most of the army is 'make work,' an extended boot camp with no actual fighting involved. You just have to earn your vote.

Another fun author is Ross Thomas. Washington reporter turned crime novelist, his books always have a political slant. 'The Fools In Town Are On Our Side' is about a political fixer whose plan to clean up a small city is to make it 'so corrupt even the pimps will vote for reform'

https://bookshop.org/beta-search?bkshp-astro=t&keywords=ross+thomas