I had the devil's own time trying tp figure out since they don't have a submission guide or anything obvious. I went to the About page, saw the editors, searched for articles by them, and requested to be added as a writer by writing a comment on one of their articles. You might also want to check out Medium Publications Await Your Political Writing. I think there are 25 pubs listed now. I usually try to write for pubs that also publish other types of articles in the hope that readers who don't normally read politics will see them.