"And why do Democratic ballots spoil so much more readily than Republican ballots? How's it done?"
"One answer could be because conservatives follow directions better than liberals, who do not believe that rules matter."
That's one answer. Another answer is that since some Dims vote at least twice, they have 2x as many chances to have a spoiled ballot.
AND... It's hard to be neat and precise when you're dead!
Of course!!