(CNN) The second Democratic presidential debate in as many days in Detroit is over.

I watched, tweeted and took a whole lot of notes. Below are the best and the worst of the night that was -- in no particular order. (My winners and losers from Tuesday's Democratic debate are here.)

WINNERS

*Cory Booker: The New Jersey senator had a very good debate. Aside from his dumb derision directed at so-called "Republican talking points" (more on that later), Booker was a happy warrior -- balancing attacks (primarily against former Vice President Joe Biden) with an optimistic demeanor. Booker spoke powerfully about criminal justice reform and immigration. And he made a very good point when he noted that Biden was trying to have it both ways when it came to former President Barack Obama -- taking credit when it works for him and distancing himself from the Obama legacy when that is more politically convenient. Booker has considerable natural gifts as a candidate -- and they shone through on Wednesday night.

*Tulsi Gabbard: The Hawaii congresswoman entered this debate as one of the least-known candidates in the field. That should change -- at least somewhat -- after a strong performance. Gabbard was reasonable but also pointed: She did real damage to Harris on criminal justice reform. She was poised and knowledgeable throughout. And she made the most of the relatively limited talking time she had, using it to talk about her resume -- most notably her service in the Iraq War. Overall, a very strong performance.

*Julián Castro: Two times is a trend. And it's been two straight debates where the former San Antonio mayor has stood out -- in a good way. He probably had the line of the night, hitting back on Biden with this hammer: "It looks like one of us has learned the lessons of the past and one of us hasn't." Castro was forceful and effective on immigration and really stuck it to New York City Mayor Bill de Blasio on how to handle the officer who choked Eric Garner. The challenge for Castro now is to qualify for the September and October debates, which could be a heavy lift given his polling thus far. If Castro can make these next two debates, he could really make noise in the race.

*Joe Biden: Boy, was this a tough call. I went back and forth on Biden's performance throughout the two hours. On the one hand, Biden was WAY more active, energetic and forceful in this debate than in the first debate in Miami. But that alone doesn't make him a winner. The truth is that this was a deeply uneven debate for the former vice president. He was, in places, quite strong -- particularly when he was going after Sen. Kamala Harris (California) and Booker (New Jersey). But Biden was much less confident when he was under attack -- especially, again, when the topic turned to race and criminal justice reform, though as the frontrunner, he did withstand fire through the entire debate. Biden also struggled in several answers to spit out the right words at the right time. And he continued to stop himself in mid-thought and immediately stop talking when his time ran out. Add it all up and I believe that Biden wound up doing *just* enough to quiet -- if not silence -- questions about whether he is up to the job. That, plus Harris' struggles, get the former vice president into the "win" column. Barely.

*Opposition research: It's not a glorious or high-profile job -- like campaign manager or press secretary -- but man oh man does it matter to the success of a campaign to have a a really good opposition research team. Both Biden and Gabbard effectively used the opposition research dug up by their teams. And Sen. Kirsten Gillibrand (New York) had a great piece of opposition research, but blew it by not holding it for the actual debate. (MUCH more on that later.) Get yourself good opposition researchers, people! They can be the difference between winning and losing.

LOSERS

*Kamala Harris: The California senator learned on Wednesday night how much harder it is to be the target rather than the targeter. From the start, Biden came at Harris on her record as California attorney general. But so did Gillibrand and Sen. Michael Bennet (Colorado). And boy oh boy, did Gabbard come after her -- dropping the opposition research book on Harris on her record in California. Harris at times effectively parried those attacks, but she didn't do it enough. On health care and criminal justice reform, she struggled to defend repeated attacks on her record; she wound up simply saying that everything everyone else on stage wasn't telling the truth about her record. Really, everyone? Harris didn't perform badly; she simply didn't live up to the high expectations that she set for herself in the first debate.

*Barack Obama: Aside from Biden, there weren't a lot of defenders on the stage of the eight years the last Democratic president spent in the White House. That was obviously a conscious choice to attempt to rob Biden of taking credit for the accomplishments of the Obama administration. But take a step back: Obama remains hugely popular among base Democratic voters. It struck me as a very strange that no one on stage not named "Joe Biden" said something like this: "Look, I love Barack Obama and admire what he did in the White House. But Joe Biden isn't Barack Obama." Or something like that. (Castro, it's worth noting, did praise Obama's handling of the economy -- and got cheered by the crowd!)

*Kirsten Gillibrand: The New York senator needed a moment. And she might have had one with her opposition research hit on a Biden op-ed in which he expressed concern about the deterioration of the family if a woman was working outside the home. But she telegraphed it six days ago! And so Biden was completely and totally ready for it -- and gave a solid answer, citing his own personal experiences as a single dad and noting that both his deceased wife and his current wife had and have always worked outside the home. I'll never understand why Gillibrand told Biden what she was going to hit him with days in advance. Giant missed opportunity for a candidate who can't afford one.

*"Republican talking points:" We started to hear this dismissive response to legitimate questions about candidates' plans on Tuesday night. And both Harris and Booker used it on Wednesday night to parry entirely reasonable questions. Make no mistake: This is a punt. It is evidence that a candidate doesn't have a good response to a hard question. And that should worry any Democrat who is looking at picking a nominee to go toe-to-toe with a street fighter like the President of the United States.

CORRECTION: This story has been updated to remove an incorrect reference to Castro's qualification status for the September and October debates.