Indiana closes polls at 6 PM to make it hard for many people to vote.
Funny enough, Indiana Republicans really don't even have much to worry about. Existing trends and gerrymandering have allowed them to lock in power for probably a good while, and playing games with early voting and poll closing times really doesn't make that much of a difference, yet they do it anyway, because that is what happens when there is no good way to contest their rule. They get comfortable making little changes to the system to disadvantage their opponents.
How does the polls closing at 6 benefit the pubs? Serious question. I'm sure it does or the rule wouldn't still be in place.
White-collar workers and SAHMs have more flexibility in getting to the polls on Election Day than people in blue-collar jobs or who rely on public transportation.