Exercise and exorcise are easily confused words. Spell-check in word processing programs doesn’t check homophone errors. What spell-check does is look for the words that aren’t in its internal dictionary, and words that aren’t spelled like those in its internal dictionary. If you used a word that exists and that word is spelled correctly, spell-check continues scanning. Spell-check doesn’t ask about context. Autocorrect on phones is also clumsy in its attempts to guess what you want to say next.
Exercise is a verb. It primary meaning is to perform physical activities for health benefits. Other meanings include performing a task or practicing legal responsibilities, like voting.
As a noun, exercise is a practice piece one performs as a closer step toward mastery, like musical exercises.
Exorcise is a verb. It means a religious ritual performed to get demons that are believed to be possessing a person to leave that person’s body.
The following sentence uses both words correctly:
Voters exercise their right to vote, but many wish they could exorcise their representatives of the foolish demons that seem to possess them once they are in office.