I don't really get the whole "party as identity" thing either. Like, people would vote Conservative or Labour for their whole lives? Really? They never consider the fact that both parties have changed significantly since, say, the 70s? To me that kind of voting is the hallmark of an unexamined political mindset. People often tend to demonise the other main party's voters, too - "the left are all stupid and spend too much money" vs "the right are all evil and want poor people to die of austerity" or whatever the current refrain is. Don't people realise that their opponents are still people, with as diverse range of motivations as anyone?
Someone who properly examines their political beliefs, through self-reflection and research, will probably end up with quite a diverse patchwork of beliefs, that aren't necessarily all put forward by the same party all the time. And at each election, they will likely vote for whichever candidate they feel will currently represent them best, which won't necessarily be the same as at the previous election.
Now, if somebody has examined their beliefs and decides that in this case, "straight ticket" or voting for the same party a bunch of times will actually get the best outcome, that's fair enough. The point is that they have actually thought about the issues at the time of the election and the particular people involved, rather than just voting for some default option...