One party doesn’t consistently benefit from low turnout, not anymore. Trump won almost exactly half of new voters in 2020. Also, “voter suppression” is a myth, just like “voter fraud.” Isolated instances but studies consistently fail to show any material effect. (E.g. no effect from voter ID: https://www.vox.com/policy-and-politics/2019/2/21/18230009/v...)
- voter suppression[1]
It doesn't really matter what percentage of the public favors X, when people who might vote for X are systematically blocked, coerced, or dissuaded from voting. And when one party tends to benefit from low voter turn-out, as is the case in the USA, it should be no surprise when very popular politicians or proposals that poll well, fail due to voter suppression.
1: https://www.votingrightsalliance.org/forms-of-voter-suppress...