From taking a jab at Rosie O'Donnell to consoling Sen. Rand Paul on a difficult night, here are Donald Trump's memorable lines from his first GOP presidential debate. (Fox News Channel)

When Donald Trump has an opinion about an issue, he feels very strongly about it. That doesn't mean it's always the same opinion.

"I'll tell you what. I've evolved on many issues over the years. And you know who else has? Ronald Reagan evolved on many issues,” he told the moderators when asked about his shift on several positions important to conservative voters. (Reagan reference: check!)

But if voter attention turns from his performance to his positions, he may have a problem. Here are three areas where he's "evolved" that came up during this week's debate.

Universal health care
Trump in a 1999 interview with Larry King on CNN: A "liberal" on the issue of "universal health care." “I’m conservative, and even very conservative. But I’m quite liberal and getting much more liberal on health care and other things. … If you can’t take care of your sick in the country, forget it, it’s all over. I mean, it’s no good. So I’m very liberal when it comes to health care. I believe in universal health care. I believe in whatever it takes to make people well and better.”

Trump at Thursday’s debate: Sure, single payer works if you're Canadian. Otherwise: no way. “As far as single payer, it works in Canada. It works incredibly well in Scotland. It could have worked in a different age, which is the age you're talking about here.” Then later: “We have to end Obamacare, and we have to make our country great again, and I will do that.”

 

Abortion
Trump in 1999 during an appearance on “Meet the Press”: "Very pro-choice...strongly for choice." “Look, I’m very pro-choice. I hate the concept of abortion. I hate it. I hate everything it stands for. I cringe when I listen to people debating the subject, but you still — I just believe in choice,” he said. “…I am strongly for choice, and yet I hate the concept of abortion. I am pro-choice in every respect, but I just hate it.”

Trump during Thursday’s debate: "I am pro-life." “And I am pro-life. And if you look at the question, I was in business. They asked me a question as to pro-life or choice. And I said if you let it run, that I hate the concept of abortion. I hate the concept of abortion. And then since then, I've very much evolved. … I am very, very proud to say that I am pro-life.”

 

Campaign finance:
Trump in his June announcement speech: The system is great, because I can get "anything." “I have lobbyists that can produce anything for me. They’re great."

Trump at Thursday’s debate: The system is "broken" because I can get things. “I will tell you that our system is broken. I gave to many people, before this, before two months ago, I was a businessman. I give to everybody. When they call, I give. And do you know what? When I need something from them two years later, three years later, I call them, they are there for me. And that's a broken system.”

 

Some candidates have been attacking Trump for sticking to controversial opinions -- not for wavering on them. Now that they're taking him more seriously, that may change.