Maybe they think that Trump is damaging the political climate and the integrity of the Republican Party so much that him getting the presidency again will lead to a long term political weakening of the pro-life movement. Also "Savior Trump" has expressed opinions about abortion this election that shows he is not as pro-life as you would like, probably causing quite a few people to change their views to his. Or they might have views in other areas that cause them to favor Harris over Trump. Maybe they think that Trump's character, his voting fraud claims (plus trying to do it himself), and his part in January 6th, makes him more unfit for president that Harris. It is relieving to me that I am not American and don't have to make this decision between two great evils.
If Bob does all this great work to save babies, then goes and votes for a candidate who undoes it all, Bob is a morally inconsistent clown. That doesn't mean I won't let him into the club, but I'm going to be very suspicious of whether he is a plant from the other side. No one has to vote for a specific candidate, but voting for someone who is openly for abortion, and will literally work to oppress and persecute us all, is not a very pro-life thing to do, and it raises big red flags. It's like claiming to support Israel, while you are funding Hamas, or shouting "Slava Ukraini!", as you supply weapons to Putin.
Or they might have views in other areas that cause them to favor Harris over Trump. Maybe they think that Trump's character, his voting fraud claims (plus trying to do it himself), and his part in January 6th, makes him more unfit for president that Harris.
It is relieving to me that I am not American and don't have to make this decision between two great evils.