re: What is the main issue that divides Reps and Dems?

It’s really more basic than that. To republicans, the government and the people are two separate entities. The government’s job is to serve the people. It is possible for government to thrive while people suffer, and vice/versa.

For democrats, the government IS the people. If the government isn’t doing well, the people are struggling too. If the government is on good footing, so must be the people. Citizens serve their government, which knows what is best for them and can correct their moral failings.