In this context, “1s and 2s” almost certainly refers to a voter classification system used in political campaigning and canvassing.
Campaigns often rank voters on a scale like this:
- 1 = strong supporter / very likely to vote for your candidate
- 2 = leaning supporter / probably supportive
- 3 = undecided
- 4 = leaning opponent
- 5 = strong opponent
So when the passage says volunteers knocked on the doors of their “1s and 2s,” it means they were targeting voters believed to be supportive and trying to make sure they actually turned out to vote on Election Day (“Get Out The Vote” or GOTV work).
The flags at the driveway ends were apparently a way to help volunteers quickly identify those supporter households in the field.