Even if one party objectively spams more than others, personal observation could be biased by (a) how your email address has been passed around and (b) subjective assessment of what constitutes “spam”.

There was once a study that "proved" Democrats were smarter because could recognize the letter W faster than Republicans. This was back during the George "W" Bush period. Basically one group was enraged at the sight of a W, so they were quick to spot it.