Threatening their job is one thing -- it's when you say that they've lost your vote _forever_ that it becomes too far, as they might feel that they have no cho

Threatening their job is one thing -- it's when you say that they've lost your vote _forever_ that it becomes too far, as they might feel that they have no choice for recompense to gain your vote back. In short, it's going too far, and even if it isn't, certainly seems like an idle threat. Saying something more like "I cannot vote for any candidate who supports this policy or any like it" is perhaps a more effective statement to make.