It is a valid question. I looked at the author's profile and while he is not from US ( Amsterdam ), his studies focus[1] appears to be on subjects that would suggest he should be relatively well acquainted with politics in US along with how they differ in terms of terminology from EU or UK. Sadly, I can't seem to say for sure how term was intended in the article itself. That said, the author does seem to reference individual US parties.

[1]https://www.uva.nl/en/profile/t/o/p.tornberg/k.p.tornberg.ht...