They might have targeted lists so you're only going door-to-door to registered democrats. My local dem org figured that out a couple of years ago so that rather than canvassing the whole area and reminding everyone that there's an important election coming up, you're focusing on turning out your voters. You're not trying to convince a Roskam voter to switch in an argument on their doorstep, you're trying to make sure Casten or potential Casten voters show up to the polls!
Not sure if the campaign is focusing on it, but Illinois makes absentee voting by mail very easy. Some states have very high hurdles, but in Illinois you just fill out a request and they send you a ballot. Here's the one for DuPage, which is where I think a majority of Roskam's district lays. Other county clerks' offices have similar pages. Hopefully the campaign is pushing the idea of early or mail/absentee voting, turnout turnout turnout!
https://www.dupageco.org/Election/Voting/37064/
For the phone banking, I got the idea from a progressive primary challenge in Delaware, could look to that as a model.
https://www.kerrievelynharris.com/phonebank/