Going into the second night of the second Democratic primary debate, only two of the candidates on the stage — former vice president Joe Biden and Sen. Kamala D. Harris (Calif.) — were averaging above 2 percent in national polls. We didn’t spot much evidence that anyone else, with the possible exception of Sen. Cory Booker (N.J.), is capable of making the leap to the status of credible contender. There was no knockout blow in the highly anticipated matchup between Biden and Harris, but Biden turned in a solid performance, going a long way to silencing critics and reassuring supporters.

We also saw just how much debates could be improved by eliminating marginal candidates. There was little to suggest Julián Castro, Sen. Kirsten Gillibrand (N.Y.), Sen. Michael F. Bennet (Colo.), Andrew Yang, New York Mayor Bill de Blasio, Rep. Tulsi Gabbard (Hawaii) and Washington Gov. Jay Inslee could plausibly compete with Harris and Biden. (Bennet was strong on substance, but his sleepy demeanor undercut his effectiveness.)

Biden oddly greeted Harris, a U.S. senator and former state attorney general, onstage with a humorous plea to “go easy on me, kid,” which coming from anyone else might have been taken as a tad disrespectful. With his opening statement, however, he was off and running. He responded forcefully to President Trump’s insult that four nonwhite congresswomen go back to where they came from: “We love it. We are not leaving it. We are here to stay. And we’re certainly not going to leave it to you."

In an extended line of questioning on health care, Harris and Biden faced off politely and substantively on their respective plans. Biden argued that the cost of Harris’s plan “will require middle-class taxes to go up” and “what happens in the meantime?” Harris made the case against the status quo: “Your plan will keep and allow insurance companies to remain with status quo, doing business as usual, and that’s going to be about jacking up co-pays, jacking up deductibles.” On points, Biden won this round, sounding informed and passionate.

Again and again, Harris brought the debate back to Biden, generally refusing to engage with lesser-known candidates. She had her hands full fending off attacks and at one point defaulted to the already tired line that those criticizing Medicare-for-all are using “Republican talking points.” (Biden shot back: “This is not a Republican talking point. The Republicans are trying to kill Obamacare. … So this idea is a bunch of malarkey, what we’re talking about here.”)

Moving on to immigration, Castro — who languishes at 1 percent in the polls — went back to his hobbyhorse: decriminalizing illegal border crossings. With help from Bennet, Biden made the case for keeping the statute as is but addressing the real issue, the flood of refugees, and removing Trump from office. He sensibly said the solution is not to decriminalize illegal crossings, although he was unwilling to say if he advised President Barack Obama against mass deportations. Instead, he shot back at those onstage slamming Obama on immigration: “To compare him to Donald Trump is absolutely bizarre.”

Booker made an early, effective entry into the debate by reminding Democrats they are up against a president who wants to take away health-care benefits. He sounded a similar note on immigration while deftly criticizing Biden for favoring skilled immigrants over unskilled immigrants. He went back and forth with Biden on criminal-justice reform, accusing Biden of having contributed to mass incarceration but getting dinged up on his own record as mayor of Newark. He gave a mature and thoughtful answer on Afghanistan, refusing to set a date certain for drawing down forces. Though he certainly helped himself, it is not clear that his performance will lift him out of the low single digits.

In the criminal-justice discussion, Harris came alive, arguing that she cleaned up the effects of crime legislation that Biden championed. She swatted away a flood of opposition research-laden attacks by Gabbard, pointing out that she actually accomplished reforms and didn’t just give “fancy” speeches. (“As attorney general, my Department of Justice became the first statewide agency to mandate body cameras and launched the first implicit bias program in the country,” she said. “I’ve spent my career working to reform the criminal-justice system.”) She also took a question about winning back Michigan to launch a full assault on Trump’s broken promises to farmers and autoworkers. She smartly walked back her prior position that she would order the Justice Department to prosecute Trump.

Biden took incoming fire but was adept at defending his plans with specifics, be it on climate change or health care. He turned the table on Gillibrand who challenged his support for working women, reminding her that he raised children on his own after his first wife was killed.

Harris gave a fiery closing speech, labeling Trump (as she does on the stump) a “predator.” Booker took a different but equally effective approach. He made a plea for “common cause and common purpose” and warned that the dream of America is under threat “from Donald Trump but not only Donald Trump.”

Certainly, Biden and Harris both had rougher patches, but they were head-and-shoulders above the others on the stage. Both showed they were more capable of appealing to the party as a whole and to independents than the Warren-Sanders duo from Tuesday night.

Unfortunately, CNN seemed to learn nothing from its horrendous reviews for Tuesday night. The same time-wasting, overproduced 25 minutes of blather at the onset, the same rigid enforcement of time constraints on candidates, the same lack of attention to foreign policy and the same crudely provocative style of questions reinforced the conclusion that not only CNN but also all of the broadcast news outlets and the DNC need to rethink the format of these events. They are too long, too disjointed and too focused on creating made-for-TV conflict.

After a serious drop in ratings on Tuesday from the first round of debates, perhaps they will abandon these counterproductive affairs.

Winner: Biden

Also winners: Harris, Booker, candidates who want to build on Obamacare

Losers: CNN, the 1 percent candidates who attacked Obama

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