No, studies on IQ have shown that the test design often assume something about the population taking the test. If you produce a test for British students in secondary school and give it to miners in Zimbabwe, then the miners will probably achieve way lower scores than is it expected. This is because the students are more used to taking tests. IQ tests have been used in this way to promote racist ideas, when the real problem is the methodology behind IQ tests.
There’s a whole book about this, “the mismeasure of man”, by Stephen Jay Gould.
Pod save America talked about this in a recent episode. There’s always a balance in the timing of these things. If you drip feed the endorsements, people might become used to it and not care. If many very famous people do their endorsements close to Election Day, it might motivate voters to actually go and vote. That’s one of the ways that those running the campaign might reason.