WASHINGTON -- The sprawling Democratic primary field has been headed toward a three-person race, and despite strenuous efforts by the trailing candidates, Thursday's debate seems unlikely to have significantly changed that.
Former Vice President Joe Biden, Sen. Bernie Sanders of Vermont and Sen. Elizabeth Warren of Massachusetts have pulled away from the pack in most national and early-state polls over the last month.
It should not be surprising that those three candidates have risen to the top of the field of more than 20: Biden, Sanders and Warren are the three contenders who came to the race with a national political brand, and they have used their campaigns to hone their messages with a clarity that none of their competitors has.
More surprising is the fact that, in a campaign that started with paeans to the party's need for youth and diversity, none of the many other candidates has elbowed into a place among the three white septuagenarians.
The problem: While some of the second-tier candidates have had solid attention-grabbing campaign moments, none has been able to translate them into durable political gains.
Thursday's debate in Houston presented those candidates with one of a dwindling number of opportunities they will get to keep a broader choice before primary voters.
It won't be clear for a week or more whether any of them had true breakout moments. But the seven rivals on the stage tried just about every tactic in the book.
Sen. Amy Klobuchar of Minnesota sought to offer moderate alternatives to the health, gun control and tax policies advanced by Sanders and Warren. Early on, she flatly declared Sanders' "Medicare forAll" plan a "bad" idea.
Former Obama Cabinet official Julian Castro repeatedly challenged Biden, including a blunt suggestion that he was losing his memory -- a personal attack that seemed to backfire, both on style and on substance.
Sen. Kamala Harris of California tried to focus on attacking President Donald Trump, not her Democratic rivals -- a somewhat surprising stance for a candidate who memorably attacked Biden in their first debate in June and enjoyed a noticeable, if temporary, boost afterward.