I'll be live-blogging here, starting at 9:00 p.m. Eastern time. Keep reloading this post (or the homepage) for updates.

Throughout the debates, Mitt Romney has stayed remarkably positive most of the time. Yet he just started cranking up the negativity against Newt Gingrich — warning of an "October surprise" and calling him "highly erratic." You can bet that the moderators will try to goad Romney into repeating those same attacks when he's standing next to Gingrich.

You can see my previous live-blogs by clicking on the "live-blog" tag.

For more live-blogging of tonight's debate, I recommend checking out TalkingPointsMemo, National Review, or Althouse (my mom).

As always, I'll write down any quotes in real time, so they might not be verbatim but I'll try to get them as close as possible.

9:08 - Romney points out that Gingrich "did resign in disgrace" after 88% of House Republicans voted to reprimand him. "His approval rating was down to 18%. . . . We suffered historic losses."

9:10 - Gingrich's response: "He may have been a good financier, he's a terrible historian." He says the only thing he did wrong was that one of his lawyers wrote one mistaken letter.

9:11 - Gingrich brings up a new attack on Romney, saying that Republicans lost governorships while he was head of the National Governors Association and lost Republicans in the Massachusetts legislature while he was governor. Brian Williams strangely doesn't give Romney an opportunity to respond. I thought the rules say if a candidate's name is mentioned, that candidate always gets to respond.

9:17 - Brian Williams asks Gingrich a ridiculous question: whether he'll shift in his views on foreign policy in order to get Ron Paul's endorsement. Williams seems like he isn't even trying to do a good job of moderating the debate.

9:19 - Romney is asked about what people will see in his tax returns. Romney brushes aside the question, briefly saying there will be no surprises and he's followed the law. "I don't think you want someone as president who pays more taxes than he's required to." But — "I'm proud of the fact that I pay a lot of taxes." Then he pivots: "What I'm really worried about is the taxes of the American people." He'd eliminate taxes on "interest, dividends, and capital gains" for everyone who makes less than $200,000 a year.

9:22 - Gingrich proposes a "Mitt Romney flat tax" — a 15% income tax on everyone. Romney asks if the capital gains tax would be 15%. Gingrich says no, he'd eliminate the capital gains tax for everyone. Romney: "Well, under that plan, I'd have paid no taxes in the last two years." [ADDED: Here's the video.]

9:25 - Brian Williams hasn't done his homework for this debate: he asks Santorum a question about why he has attacked Romney over Bain Capital, and Santorum has to say he hasn't made any of those attacks. Romney agrees.

9:29 - Romney goes after Gingrich on his work for Freddie Mac: "They don't pay historians $25,000 a month for 6 years. That's about $1.6 million. They didn't hire you as a historian. They hired you as a consultant. . . . And you were hired by the chief lobbyist of Freddie Mac. . . . You could have spoken out aggressively. You could have said, 'This is wrong, this needs to stop.' But instead you were being paid by them."

9:35 - My mom says Gingrich "looks tired and badly made up."

9:44 - Brian Williams asks, "What do you do if you find out that Fidel Castro has died?" Romney: "First of all, you'll thank Heavens if Fidel Castro has met his maker." Gingrich says Castro won't "meet his maker" but will go to "another place." So Gingrich seems to think "meet his maker" means "go to Heaven." I thought it just meant "die."

10:04 - The candidates are asked why it's OK for them to run ads in Spanish, yet they want English to be the national language, which would mean the ballots would be only in English. Gingrich says he's happy to cater to any ethnicity in his campaign, but the country should be unified with an official language. Ron Paul says he's in favor of English as the official national language, but the federal government shouldn't stop states from doing whatever they want in other languages.

10:07 - Rich Lowry asks:

why would anyone not professionally obligated still be watching this debate?

10:19 - Santorum is asked why he supported congressional intervention after a judge ruled that Terri Schiavo had been in a vegetative state for years. (Apparently they're bringing this up because it happened in Florida, and Florida is the next primary.) Santorum says he didn't support congressional intervention; he supported intervention by a federal court. So why did he support federal judicial intervention? He says Schiavo's parents happened to be from Pennsylvania, and they talked to Santorum and convinced him that the decision should be reconsidered by a different judge. But how was this Senator Santorum's decision to make?

10:25 - Question: "Why didn't the Bush tax cuts work?" Gingrich says they did work, because after the attacks of September 11, the economy would have gotten even worse if it hadn't been for those tax cuts. So why doesn't he say President Obama's policies have "worked" because if not for them, after the crash of 2008, the economy would have gotten even worse?

10:34 - Brian Williams inexplicably asks Santorum a second question about Romney's record at Bain Capital, after Santorum already made it clear that he hasn't made any of those attacks in his whole campaign! Of course, Santorum refuses to answer the question and uses his time to say whatever he wants. Again, Brian Williams is apparently not even trying tonight.

10:38 - Romney brags that Ted Kennedy "had to take a mortgage out on his house" in order to beat Romney in the 1994 race for the Senate. This is a very mean-spirited attack on someone who recently died, and I wish Romney would drop it. It accentuates the image of Romney as a Machiavellian tycoon.

That's all. That was a lackluster debate all around. I've seen almost every debate in these primaries, and Brian Williams may be the worst moderator I've seen.