When is the next occurrence the state of Indiana will carry Democratic in a U.S. presidential election?
With exception of 2008, Allen County has carried for the winner of Indiana in every U.S. presidential election since 1912.
Since we're looking at historical voting patterns, we should also assume Elliott County will vote blue (like it has in all but two presidential elections in its entire history) and that Orange, Riley and Cobb Counties (all historically Republican) will vote red.
The way a county has historically voted doesn't matter much in the case of suburban/urban areas that are shifting leftward. Admittedly, Allen hasn't shifted as much to the left as places like Hamilton County, but it's shifting leftward. It voted to the left of IN in 2020 and given its (sub)urban nature, will continue moving leftward as IN remains stagnant. Soon, regardless of whether IN flips (which it most likely won't), Allen County will be going blue.