<p>I might have to cancel an interview because I have a debate tournament on the same day as the interview. Would that ruin my chances?</p>
<p>Shouldn’t. Cancelling sooner rather than very close to it is better. If you reschedule, don’t cancel again.</p>
<p>I would call the school ASAP, explain the reason for the conflict, apologize for the inconvenience, and reschedule. It shouldn’t be a problem.</p>