Under allocation of resources in populous Democratic-leaning areas is a tried and true voter suppression tactic.
And it it very effective.
Beware overconfidence. When coupled with long lines, it is a turnout killer.
Many simply cannot afford to wait. Others think "she's winning anyway" and give up. In phone banking or canvasing, anyone who hasn't voted yet needs to be prepared, and encouraged to be persistent and overcome hurdles that are going to be erected -- and be ready with a plan for waiting -- child care, time off work, whatever a person can possibly do.
We MUST stop cheering long lines. It isn't driven by "unprecedented turnout." It's bad planning and we should be furious about it. Any federal voting rights legislation should include substantial fines for counties who fail their residents and subject them to long lines. We need to make under-allocation of resources costly.
(I can't put my hand on the study but I recall an analysis several years ago that indicated that, when all is said and done, long lines are actually more strongly associated with suppressed than high turnout.)