Trump came to the debate with several points ready to address the abortion issue. Some of what he said was wrong.

For example, he said there was unanimous opposition to Roe v. Wade before it was overruled..

Fifty-one years ago, you had Roe v. Wade, and everybody wanted to get it back to the states, everybody, without exception, Democrats, Republicans, liberals, conservatives. Everybody wanted it back. Religious leaders.

And what I did is I put three great Supreme Court justices on the court, and they happened to vote in favor of killing Roe v. Wade and moving it back to the states. This is something that everybody wanted.

He also said that under Roe v. Wade babies could be legally killed after they were born..

BIDEN: . . . And if I'm elected, I'm going to restore Roe v. Wade.

TRUMP: So that means he can take the life of the baby in the ninth month and even after birth, because some states – Democrat-run – take it after birth. Again, the governor – former governor of Virginia: put the baby down, then we decide what to do with it.

So he's in – he's willing to, as we say, rip the baby out of the womb in the ninth month and kill the baby.
Both of Trump's statements quoted above were so false that he must have known he was saying things that were untrue.