(Reuters) - Republican presidential candidates met on Tuesday in Las Vegas in the eighth of a series of debates.

Here are some of their comments:

MITT ROMNEY, FORMER MASSACHUSETTS

On Herman Cain's 999 tax plan

"I like your chutzpah on this, Herman, but I have to tell you, the analysis I did, person by person, return by return, is that middle-income people see higher taxes under your plan. If it's lower for the middle class, that's great. But that's not what I saw."

In exchange with Rick Perry over illegal immigration

"Would you please wait? Are you just going to keep talking...("Yes, sir," Perry responds). Would you let me finish with what I have to say?... This has been a tough couple of debates for Rick, and I understand that. And so you're going to get testy."

HERMAN CAIN, FORMER GODFATHER'S PIZZA CEO

Defending his tax plan

"The reason that our plan is being attacked so much is because lobbyists, accountants, politicians, they don't want to throw out the current tax code and put in something that's simple and fair. They want to continue to manipulate people with a 10-million-word mess."

On immigration

"I believe we should secure the border for real, and it would be a combination of a fence, technology, as well as possibly boots on the ground for some of the more dangerous areas. I don't apologize at all for wanting to protect the American citizens and to protect our agents on the border, no... I believe in let's solve the whole problem. We must shut the back door so people can come in the front door."

RICK PERRY, TEXAS GOVERNOR

On Cain's tax plan

"Herman, I love you, brother, but let me tell you something, you don't need to have a big analysis to figure this thing out... I'll bump plans with you, brother, and we'll see who has the best idea about how you get this country working again."

On illegal immigration

"Mitt, you lose all of your standing, from my perspective, because you hired illegals in your home and you knew about it for a year. And the idea that you stand here before us and talk about that you're strong on immigration is on its face the height of hypocrisy."

RON PAUL, TEXAS REPRESENTATIVE

On Cain's 999 tax plan

"It is a regressive tax. So it's very, very dangerous. And it will raise more revenues. But the gentleman asked the question... what are you going to replace the income tax with? And I say nothing. That's what we should replace it with."

MICHELE BACHMANN, MINNESOTA REPRESENTATIVE

On immigration

"Well, I think the person who really has a problem with illegal immigration in the country is President Obama. It's his uncle and his aunt who are illegal aliens who've been allowed to stay in this country, despite the fact that they're illegal."

On Obama's foreign policy

"Defense spending is on the table, ... now with the president, he put us in Libya. He is now putting us in Africa. We already were stretched too thin, and he put our Special Operations Forces in Africa."

RICK SANTORUM, FORMER PENNSYLVANIA SENATOR

Says Perry and other opponents backed TARP

"You supported it. Governor Romney and Herman Cain all supported the TARP program... You guys complain about Governor Romney flip-flopping. I mean, look at what's going on here. I mean, the -- the bottom line is, you all supported it, you all started this ball rolling, where the government injected itself in trying to fix the market."

(Compiled by JoAnne Allen; editing by Alistair Bell)