There is no such thing as an “undervote,” it’s a term that USA Today and AP made up in 2000 while trying to help steal an election for Gore. There is who voted and who did not. There is no under - or over - voting. PEriod.
In the old days of paper ballots, if you checked two boxes and were entitled to just one, the votes for that office were disqualified.
undervote is a technical term for a ballot selection being left blank, i.e. the voter chose not to choose either candidate. It’s common and the term has existed since I studied statistics in college in the eighties.
A 4% undervote is not an unusual percentage and is not suspicious in and of itself.
I always write in a cartoon character when I don’t like the choices for the simple reason that leaving a section unmarked opens the door for dishonest election workers to fill it in for you.
This article is setting up expectations in order to enable exactly that. Doctor the undervoted ballots and claim it was a machine error in reading them, after the inevitable recount magically changes the outcome.