Sen. Kamala Harris, D-Calif., and former Vice President Joe Biden participate in the second of two Democratic presidential primary debates hosted by CNN Wednesday, July 31, 2019, in the Fox Theatre in Detroit. (Paul Sancya)
Opinion writer

Time is running out for most of the 20 candidates who have appeared in either of the Democratic debates so far. Unless they qualify by Aug. 28 for the September debates — meeting the 2-percent-polling and 130,000-donor thresholds — they’ll be off stage, out of sight and, in all likelihood, kaput as presidential hopefuls. The few top contenders, however, have some time to refine their messages and improve their debate performances. There are a great many voters who haven’t yet tuned in, or will forget early performances if better ones follow.

Free advice is what you pay of it, but here goes:

Former vice president Joe Biden certainly improved between the first and second debates. However, he has three remaining challenges. First, he must disabuse voters of the notion he’s about going back to the past or simply perpetuating President Barack Obama’s legacy. He’ll win if he convinces voters that he can build on it, improve it, take it to the next level, etc.

Second, Biden must push back against claims made by his opponents that he is playing small ball. He’s playing winning ball and not succumbing to the Twitter fantasyland that believes certain proposals — many of which some Democrats don’t support — are going to ever become law. (If Sen. Elizabeth Warren “can’t understand” why Democrats would to champion reasonable measures, Biden can explain, “Because we have an obligation to help real people, not get ‘likes’ on Twitter.”)

Third, Biden needs a better response when opponents dredge up an op-ed or a vote or a comment from the past that, in 2019, doesn’t sound too great. One approach is: “You can worry about 40 years ago. I’m focused on the future.” Alternatively, he could say, “I’ve learned a lot, especially after eight years serving as VP for President Obama.” All that said, he comes out of the second debate stronger than he was going in; and with each passing month, his chances of being the nominee increase.

Sen. Kamala D. Harris (D-Calif.) was never going to match her near-perfect performance in the first debate, if for no other reason than she’d become a target for lesser candidates. Now that she is in the big leagues, there are two things she can do to improve on the debate stage and elsewhere. First, she must be able to explain her health-care plan succinctly. She’s done that for other her other proposals, but fuzziness on health care still plagues her. She needs to be able to tick off the four or five things her plan does and how it fixes one or more specific problems with Obamacare. Second, when confronted with a fact-based attack about her record as a prosecutor, it’s not good enough to say “that’s false” or “that’s wrong.” She needs to crisply answer the charge and then explain her overall record. If there isn’t a good response, she would do well to concede error and say she’s learned from the past.

Then there is Sen. Elizabeth Warren (D-Mass.), who arguably had the most consistently strong showings during the two debates. However, she cannot continue to response to every criticism by claiming “that’s a Republican talking point” or “you just don’t want to do big things.” Answer the charge. If she can rebut claims that her plans would cost an astronomical amount, would be disruptive to ordinary people’s lives, or would deprive people of choices, she should present her case, not insult the critic. In this regard, she’ll need to prepare for the inevitable question: “What are you going to do when Congress says no?” A little less moral certitude and a little more presumption of her opponents’ good faith would go a long way toward convincing skeptical Democrats that she’s not a rigid ideologue like Sen. Bernie Sanders (I-Vt.).

As for Sanders, there is little one can suggest to someone unwilling to deviate from the tone and substance of his 2016 campaign. He refuses to make himself more personable, or to reveal his own experiences. He lacks the depth of knowledge and passion for issues other than health care and socking it to Wall Street. Maybe he could at least stop screaming?

That brings us to South Bend, Ind., Mayor Pete Buttigieg. He has also been a consistently strong performer in two debates and during numerous interviews and town halls. It is no small feat to make the leap from being an unknown and unpronounceable mayor to being a top-tier presidential contender. His calm, methodical demeanor and his ability to invoke religious-based values, coupled with a policy nerdiness (this is a good thing!), are pluses. By refusing to go down the Sanders/Warren road on health care, and by adhering to a grown-up foreign policy vision, he may be primed to move up if Biden eventually does falter, or if the three more-aggressive progressives fall away. He must, however, to do more to assert himself into the back-and-forth on the debate stage. And finally, he has to continue working to win over critical African American voters. Frankly, if the other candidates want to dump all over Obama, he might consider squarely defending Obama’s legacy — and reminding voters that Obama is the only Democrat to win Indiana in 55 years.

Read more:

Karen Tumulty: How Elizabeth Warren won both nights of the Democratic debate

Marc A. Thiessen: Forget moderates vs. radicals. The debate was a left vs. far left brawl.

David Ignatius: The debaters eerily sounded like ‘America First’ Democrats

Josh Rogin: Tulsi Gabbard’s Syria record shows why she can’t be president