Of course what the Democrats need to do is encourage absentee voting. That is something the Republicans have been reluctant to go after since a lot of their electorate uses it as well.
What Democrats
really need to do is pass electoral reform causes in states where they have fairly comfortable control in. Automatic voter registration or even so far as compulsory voting. Democrats shouldn't play defensive with these things, they should fight back against voter restrictions by passing laws that dramatically open up the amount of voters. There's literally no reason we
shouldn't have automatic voter registration, it works great and there are several working systems we could replicate.
On the national level Democrats should make it a top priority to have an independent electoral oversight organization actually worth a damn. It should be rather telling if Republicans oppose that. (And they inevitably would.) Canada is a pretty good model for both the registration and a potential electoral watchdog group.