It’s one thing if the President develops the disease while in office, and that’s mostly irrelevant. But I don’t think a candidate with an a priori serious chronic illness will get elected simply as a matter of prejudice. At least where IBD is concerned, we know it’s mostly prejudice. We already know someone with IBD could be up to campaigning and serving as President, because both Eisenhower and Kennedy did so. Incidentally, Kennedy took DOCA, an early form of prednisone, for his colitis; the DOCA gave him (or triggered) Addison’s.

I don’t think Kennedy could win today, and I doubt Eisenhower would even be allowed in the military.

Reagan probably had the beginning stages of Alzheimer’s during his term as President. Nixon was severely mentally ill. Kennedy had Addison’s Disease, and was on Prednisone.

I think it is somewhat unlikely for a IBD patient to get elected President, but only because the campaign trail induces bad diet, worse work habits, irregular medicine routines, etc, which are likely to lead to flares. Whether an IBD patient would be up to the rigors of a Presidential campaign is an open question.

However, I have no doubt that I will live to see the sad day when a sitting President gets diagnosed with IBD or cancer, or some other horrible disease. People like Paul Tsongas almost won in 1992–Tsongas had recurring cancer a few short years later.

If the disease is in remission, I do not see it as an obstacle to getting elected. Heck, Joe Biden has some serious, serious health problems (two brain surgeries) and he was elected Vice President without much fuss over his health records.