A voter should not be forced to vote for a contested race after declining to do so the first time. If he/she is uncomfortable voting because of lack of knowledge about the two candidates, that should be accepted as much as a vote is for the other races.
I think the author is wrong about that. The ballot is returned if the vote is indecipherable; if there is a mark for both candidates, a single mark (a filled in oval) is not sufficiently dark, or marked up white space near the ovals. Generally, if the dems run out of "found" ballots, the 206 (or whatever it is down to today) has a very good chance of standing up. Unlike rat election judges, the mistakes made by machines are rare, and tend to balance out.