Twitter can’t tell us whether, or how, Sunday’s debate between Joseph R. Biden Jr. and Bernie Sanders might change voters’ minds. But it can give us the perspectives of some of the people with expertise on primary races: veteran campaign strategists, consultants and analysts.

Here is a sampling of their reactions, both to the candidates’ overall performances and to their exchanges on key topics.

Joe Biden

Mr. Biden’s commitment to choose a woman as his running mate earned him praise, as did his responses to questions about the coronavirus. But he also had some shakier moments, and some strategists thought that given his solid lead in the primary, he should have focused more on contrasting himself with President Trump than with Mr. Sanders.

“.@joebiden is looking very good here. Strong. Command. Rising to the moment of crisis. Best he’s been in 11 debates.” — David Axelrod, director of the University of Chicago Institute of Politics and former senior adviser to President Barack Obama “Smart of Biden to keep bringing the focus back to RIGHT NOW. This is a moment of urgency & folks are desperate for immediate solutions, not academic debates.” — Jesse Lehrich, former foreign policy spokesman for Hillary Clinton “Joe Biden’s answer to the question on how he will get the support of Latinx voters, who have overwhelmingly voted for Sanders, was inadequate. Was it me or did it sound like he didn’t care that Latinx voters aren’t voting for him?” — Cristina Jiménez, co-founder and executive director of United We Dream “Biden has been surprisingly negative, given current polls & delegates & fact that coronavirus news is likely to overwhelm the debate & the primary. I expected more of a pivot to the general & more Trump attacks.” — Matt Grossmann, director of the Institute for Public Policy and Social Research at Michigan State University

Bernie Sanders

Commentators thought Mr. Sanders, too, had a strong performance over all, but they did not think he changed the course of the race, which has veered sharply toward Mr. Biden. He also drew some criticism for his continued defense of his controversial remarks about Fidel Castro.

“Bernie Sanders had the better #DemDebate performance tonight, but @JoeBiden won the debate by committing to a woman VP. The Democratic primary is over.” — Frank Luntz, Republican consultant and pollster “On climate, there are a lot of people — especially young people — who simply want to hear @JoeBiden say that it is an existential threat and would be a sacred mission for his administration. @BernieSanders speaks in moral imperatives, and Biden responds in a programmatic way.” — David Axelrod “I’m not sure what Bernie gains by the ‘sometimes dictators do good things’ defense.” — Carol McDonald, Democratic strategist and former deputy political director for Hillary Clinton “That was Bernie’s best closing statement in any #DemDebate this cycle.” — Laura Belin, Iowa political commentator

Coronavirus

The first and most important subject Sunday night was the coronavirus pandemic, which has killed thousands of people worldwide and, in the past week, shut down much of American society. The candidates took different approaches: Mr. Biden emphasized his experience responding to the swine flu and Ebola outbreaks during the Obama administration, while Mr. Sanders argued that the pandemic proved the need for programs like “Medicare for all.”

“Sanders with a more coherent initial response on COVID-19 than Biden — and meets Dem voters where they are by criticizing the president’s response as insufficient.” — Dave Wasserman, editor at Cook Political Report “People might get tired of hearing about the Ebola example, but the learned lessons from experience is critical to save lives — especially if we are dealing with something worse.” — Amanda Renteria, interim president of Emerge and former national political director for Hillary Clinton “Sanders doing a really good job connecting his core #M4A [Medicare for all] message to #coronavirus. A really good contextualization of how he will govern.” — Jess Morales Rocketto, political director of the National Domestic Workers Alliance “This entire debate so far has really been a series of questions about crisis management, through the prism of coronavirus. In short, Biden’s answer is leadership. Sanders’ answer is ideology.” — Mo Elleithee, executive director of Georgetown Institute of Politics and Public Service and former Democratic National Committee spokesman

Running mates

The most unexpected news of the debate came when Mr. Biden pledged unequivocally to choose a woman as his running mate if he wins the nomination.

Asked if he would make the same pledge, Mr. Sanders said he would probably choose a woman but did not commit definitively the way Mr. Biden had, saying instead that he would “in all likelihood” do so and that “my very strong tendency is to move in that direction.”