Uh, the article says nothing about senators.
For five years now, the Intercollegiate Studies Institute has been conducting a national survey to gauge the quality of civic education in the country. We've surveyed more than 30,000 Americans, most of them college students, but also a random sample of adults from all educational and demographic backgrounds.
Included in the adult sample was a small subset of Americans (165 in all) who, when asked, identified themselves as having been "successfully elected to government office at least once in their life" -- which can include federal, state or local offices.
Who knows who these random people are, but it seems kind of obvious that they're just local randoms. If they're understanding of basic politics is so meh then why should we even trust they know what "successfully elected to government office" means.
I just thought that my thread title was more catchy than "You know the constitution better than 165 successfully elected federal, state or local officials?" Anyway, you can read the full report and look at the methodology
here. Everything looks on the up and up to my untrained eyes, but I'm not a statistician. However, We've all read horror stories about members of Congress being unable to answer basic constitutional questions, and now there's some data to confirm why.
EDIT:
There's also an expanded quiz:
https://www.americancivicliteracy.org/resources/quiz.aspxMy score:
You answered 31 out of 33 correctly — 93.94 %
Average score for this quiz during January: 74.6%
Missed the one about Roe v. Wade and the final one about taxes.