"I don't agree with that aspect, but I do respect her — her views," McCain said of Palin's stance on abortion rights, which doesn't allow for abortions even in the case of rape of incest.
McCain said she and her husband do not favor a constitutional amendment to ban abortion.
"It is a state issue. We both believe that these are state issues, and that the states should make the decision."
As for abstinence education, which Palin favors, McCain favors for a more comprehensive approach.
"I taught my children at home about this. I believe that the message should come from the parents and from the family. With that said, our school offered sex education, and I was a large advocate for all — also offering abstinence in sex education. I believe it's two-fold, and I think all of it should be taught," she said.
McCain said she believed in her heart "a while back" that Palin was the right choice to be her husband's vice presidential running mate.
"I really did," McCain said. "You know, I knew all the other people very well. And of course, we knew her. And I just, in my own head, just kept coming back to her as did my husband, obviously. They're mavericks."
McCain told Sawyer that Americans should stay tuned for her husband's convention speech Thursday night, which she has already heard.
"It's marvelous," said McCain, who added she sometimes gives her husband pointers on his speeches.
"He sometimes takes my advice and sometimes doesn't," she said.
But after what some called a dynamic performance by Democratic presidential nominee Barack Obama during his convention speech last week in Denver, McCain wouldn't be able to compare whether her spouse's speech is better than the Illinois senator's because she didn't watch it.
"We were traveling," she said. "Honestly, we were out and about and didn't get a chance to see it."
As the convention focuses on John McCain tonight, so will his wife, who said she can tell when he's nervous.
"I can tell when he's nervous, or when he's bored, too," she said. "But he's really in good shape for this speech. He's excited about giving it."
McCain too is enthused about formally introducing herself to the nation. She speaks ahead of her husband this evening to ensure people get to learn more about her.
"I'd like people to know what makes me work and what makes me tick, and who I am, what I'm all about. And where I came from because I have an interesting story to tell as well. And that it combines the two of us and makes us a couple, and maybe what we will represent to us," McCain said.
ABC News' Diane Sawyer, Michael S. James and Eloise Harper contributed to this report.