Voting for someone who claims to be “Christian” means nothing. President Obama makes such a claim. I think he makes that claim because he knows it is helpful if you want to win elections.
Jimmy Carter was a Democrat - I don’t remember that much about him, but as a Democrat, I would assume he was pro abortion, but, I could be wrong.
Can a born-again Christian support abortion, homosexual behaviour, etc? Personally, I don’t think so.
Yes, Jimmy Carter was, and is, pro-abortion. He sure fooled a lot of Christians to vote for him, though, particularly that first election, by quoting from the Bible and telling everyone that he was a Born-Again Christian.