I heard a State Senator interviewed by Brian Williams explain what happened to him in his manual recount in Texas - a Republican! But no one is discussing this reason for the dimpled chad and it is not being considered by the election boards:

My letters to all the papers and TV shows:

Another reason for the pregnant chad: When a chad that is punched out does not fall through to the collection bin but gets lodged in the chute, other chads build up behind it until the chad from the ballot is no longer getting punched out. It becomes indented by the stylus until someone with some strong voting body english pushes the build up down into the collection box. This is a voting machine error as the chad build up is caused, not by the voter, but by an inherent defect in the design of the machinery.

This was explained by a REPUBLICAN State senator from Texas, who won because of the Texas law.

Think about using a hole punch. After you have punched a lot of holes, the paper builds up in the hole punch and you aren't able to punch properly until you clear the stack of undiscarded, punched out paper rounds. The same holds for the chads.

Do we know how many thousands of people only voted for President and not for the other candidates? If the chad build-up occurred in the presidential column, it may have impacted only that race. So the other races would have punched cleanly by subsequent voters.