Seconding both Emory QSS and Penn State SoDA or Public Policy.
tOSU has a good Data Analytics program too, as does nearby Denison U. Data Analytics | Denison University Denison’s Lugar Program is also top-notch for students with an interest in poli sci.
Since you’re already looking at Purdue, another Indiana option is the Public Policy Analysis major at IU, which differs from other majors in this field in that it’s housed in the highly-regarded Kelley School of Business. I don’t know whether the business spin would be a plus or a minus for you, but fwiw.
URochester could be worth a look as well; their flexible curriculum structure lends itself particularly well to the kind of interdisciplinary focus your kid is looking for: Undergraduate Program : Goergen Institute for Data Science and Artificial Intelligence : University of Rochester There are multiple major/minor/concentration options on the Poli Sci side.
The problem with going to UDub as a poli sci major and intending to minor in data science is access to classes; computational classes can be quite impacted and minors don’t get preference for course enrollment. It might be worth considering the riskier path, admissions-wise, of applying as an Informatics major and adding the poli sci piece in once there.
Likewise, consider the Informatics major at UC Irvine as well.
You might look into the options at the Claremont Colleges. I don’t think you stated the student’s gender, but if female, Scripps has been investing heavily in their Data Science minor, which can be combined with Poli Sci (strong course offerings across the whole consortium) or a related interdisciplinary major like Environment, Economics & Politics. Claremont McKenna is known for its poli sci, econ, and PPE majors, and also has a data science major Data Science - Claremont McKenna College - Modern Campus Catalog™ . Pitzer and Pomona both have data science minors and strong poli sci, as well.
Your student has a strong record; a lot of good options should be open to them, especially given the lack of cost constraints, so I think they can afford to dig a bit deeper in terms of exactly what they’re looking for (both academically and in terms of campus life) and narrow down what looks like the best fit. When push comes to shove, they’ll have solid options in the CA public system (as you say, Data Science at Riverside will be a safety and could work well), so the question is what schools you’d consider worth going farther and/or spending more - in some cases much more.