This, in the article:
“ The dramatic increase comes after new election legislation in the commonwealth and efforts by both candidates to mobilize their partisan bases to vote early. ”
Repeat: BOTH candidates.
This, also in the article:
"And data suggests that he has an edge over his GOP opponent in pre-Election Day voting. Democrats make up 53% of the 1.1 million who sent in their ballots early, according to TargetSmart. That compares with 30.9% for Republicans."