Should one include irrelevant background on CV after career change?
The context for what the CV is going to be used for is key. I have a single CV that includes "everything" since I started grad school and selected things from before then including seemingly unimportant part time jobs. Having a long CV makes it easier for me to create short CVs because it means I need to delete things instead of remember things.

For your intended context, I would not include the work experience, but might include the degree in politics. Including that degree will likely lead people looking at your CV to think you are older (which might be a pro or a con). If you are worried about age discrimination, I would drop it completely.