> 9 members with IQs under 70 (i.e. mentally handicapped) > 52 members with IQs under 85 > 217 members at or under an IQ of 100 > 370 members with an IQ below the (presumptive) current congressional average of ~115
Congress is terrible, but it's hard to imagine it could be improved by making it less intelligent.
If you could incorporate the OP's point about limited eligibility and "directly select candidates at random for positions from an eligibility pool", then a "random" process would likely be superior to elections.
In fact, I would argue that idiots in elected bodies are a lot more likely to do damage than random idiots, because they are more likely to be narcissists, and being elected boosts their sense of self-worth. And of course, the most damage is often caused by the most intelligent of them, because the main problem is acting in bad faith, not a lack of wits.