When people do not like a candidate, they flock to the other candidate, overlooking all of that other candidate’s shortcomings. As a result, two candidates who are disliked by most people have got so much support nonetheless.
The possibility of letting the candidate one dislikes the most get elected has been keeping people from stopping their support for the other candidate even though they know that this other candidate is not all that great.
There are several problems with voting for the lesser of two evils. One is that you are still supporting an evil. Two is that your vote is used to elect a candidate who is unqualified. Three is that by supporting one evil, you are inviting or pressuring some people to support the other evil (to counter your support for the evil that they dislike more) which is against your own wish.
If we do not want to see an unqualified candidate getting ahead in the race, stop supporting all unqualified candidates.
Have some respect for people in the opposite camp and stop your support for the candidate that they do not like for the right reasons.