if i were running for office, and my opponent were dying of cancer, i would do everything i possibly could to ensure that voters were aware of the facts in the matter - so they don't vote for a terminally ill person that is unable to carry out their term.

"you should not vote for her because she has stage 4 cancer" is an absolutely valid argument. and, if you think there is something wrong with that because it harms your moral dignity or something, you're an irrational buffoon - a bleeding heart, even.