Earlier quoted context omitted.
People voting D or R because that’s their tribe rather than because they want those policies is an example. I know a lot of people who vote without even really reading what’s on the ballot. They just go with whatever option has D next to it. Others do the same but for R. Personally I can’t vote so it’s mostly an interesting phenomenon to observe
I feel like calling that “identity” muddles the term, as identity politics generally refers to categories like race and gender, and maps to feelings on issues such as abortion and the Black Lives Matter movement. To attempt to be helpful, I’d suggest that what you’re referring to is more of an issue of uber partisanship than identity per se.
You can see this in how people say “I am a democrat/republican”. They don’t say vote or belong to or member of, people very explicitly talk about it as an identity and both or all parties encourage that.