10:06p.m.: Herman Cain must be so very happy Rick Perry got into the presidential race. Wednesday night, Cain did apologize for comments about a woman -- not his accusers, but Nancy Pelosi, whom he called "Princess Nancy." In the post-debate show on CNBC, he said, "That was a statement that I probably should not have made." But no one was thinking about Cain's woman problem after the painful seconds in which Perry couldn't remember which government agency he'd abolish. In the spin room, Perry said, "Bottom line is, I may have forgotten energy, but I haven't forgotten my conservative principles," NBC News reports. Michele Bachmann was moved to say she felt bad for him afterward.

Meanwhile, Romney won tonight by default by going mostly unnoticed. Though, he did have a brief flub of his own, where he almost misstated how long he'd been married to his wife just after touting his "steadiness and constancy." 

But the story of the night is Perry's struggle. The Atlantic's James Fallows ranks Perry's mistake up there with the greatest debate gaffes of all time. Many, such as Political Wire's Teagan Goddard, see his "inability to remember his own talking point" as the end of his campaign. National Journal's Marc Ambinder thinks Perry's consultants convinced him that running for president would be easy, and that's why Perry thought he could coast.

9:27p.m.: Everyone's talking about Rick Perry forgetting which federal government agency he would eliminate, even after trying to get an assist from his neighbor on stage, Ron Paul. It seems highly likely that will be the moment from this debate that we rewatch over and over the rest of the week.

A clip of Perry's stumbling response:

And this photo is circulating:

9:05p.m.: At an hour in, it seems like no one wants to attack Herman Cain on the sexual harassment charges. Any question about them is loudly booed by the audience. Maybe that's giving him just a little too much confidence, as commenter FloridaInternational notes -- he called House Minority Leader Nancy Pelosi "Princess Nancy," which sounds a little bit off given what he's been accused of in the past nine days. Newt Gingrich has been playing to the talk radio crowd in attacking the media and the CNBC moderators -- though Maria Bartiromo has been pushing back. Mitt Romney is looking a little tired. Rick Perry said of entities seeking bailouts -- be they countries or banks -- "if you're too big to fail, you're too big." Commenter Perfect Circles wonders whether this means a couple struggling American states should be split up.

7:05p.m.: We've got a couple programming notes for the live blog of tonight's debate, which starts at 8 p.m. on CNBC: You have two hosts -- Elspeth Reeve and Rebecca Greenfield -- and this time we're going to try liveblogging in comments. That means you can add your two cents right along with us. All you need to do to join in is to sign in with Disqus, and post. We'll feature some of the main highlights and best comments up here, but the main action is down below. Join us!

5:54 p.m.: Tonight's Republican primary debate in Detroit will be about the economy, which means it will give Herman Cain a chance to talk about something other than how tall various women are. Cain's most popular proposal so far has been his tax plan, so he might be able to remind viewers why they started paying attention to them in the first place. On the other hand, Cain says he doesn't like to play by the old media rules, so maybe he won't duck the sexual harassment controversy at all. Rival Michele Bachmann is a diminutive lady -- perhaps Cain will ask for her assistance in explaining one more time how tall his wife is relative to his chin. He could demonstrate how it was all so innocent. So far no pundits are recommending that course of action -- those inside-the-box thinkers -- but those who love reality TV can dream.

Most of Cain's rivals will probably avoid the sexual harassment allegations, First Read predicts, because they want Cain's voters and don't want to make them mad. But The Washington Post's Chris Cillizza says Michele Bachmann might be ready to attack Cain, having already promised voters that she wouldn't blindside them with "surprises." Rick Santorum might go after Cain too, Cillizza says. As for the other candidates, CBS News reports that Rick Perry has been through several study sessions so he can perform better in this debate than in the earlier ones this fall. Perry's also been trying to show his nicer side, which means maybe we won't get a chance to see Perry and Romney yell at each other all night as we did at the Las Vegas debate. And Jon Huntsman, who's being considered as the last-chance Not Romney candidate, needs to stand out, The Washington Post's Nia-Malika Henderson writes. He needs to " drop the broad, sweeping answers to basic questions" and the lame jokes, she says.