So in California. They give instructions on how ballots should be placed in the envelope. When you do that — the Democrat candidate aligns with a visible hole. Which means, when processing the ballots the person sorting them can tell if it is a Democrat Ballot or a ballot voting for someone else. That is significant. Now think about the time it takes to process California ballots. Who is it that in some areas (LA County Mayoral Election) you have a mass dump of 24k ballots all for one candidate and not another? How I imagine this works. A ballot facility takes all the ballots that have that mark filled out and separates them. Then they process them individually. The others ballots then are processed separately. An initial count of a batch should give a rough estimate of Democrats versus Republican votes and give a probability of who is leading out of that batch. This is before any ballots are actually counted. This is a great method to know who is leading in the ballots prior to processing the ballots, especially when this is a numbers game.