Senator Elizabeth Warren, the only person on the stage Wednesday polling in double digits, was expected to be the star of the first Democratic debate — and for the first half-hour, she was. But by the end, several lower-polling candidates had taken the spotlight: Senators Cory Booker and Amy Klobuchar, and especially Julián Castro.

Twitter is a bad gauge for public opinion, but a decent source for the assessments of political experts, including those who know the stakes of debates best: veteran campaign strategists and consultants from both parties. Here is a sampling of their responses.

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Warren owned the first quarter

In the first segment, which focused on the economic issues on which Ms. Warren is particularly passionate, there was little contest.

“Twenty minutes in and from the economy to health care, @ewarren is simply crushing the debate stage.” — Adrienne Elrod, former senior adviser to Hillary Clinton