But the 12-candidate milestone had yet to be reached, setting up a challenge for the event’s moderators, the CNN anchors Erin Burnett and Anderson Cooper and the national editor of The New York Times, Marc Lacey.

[What question would you ask the Democratic candidates? Our debate moderator wants your suggestions.]

The Ohio debate, on the campus of Otterbein University, will feature the 10 candidates who appeared at last month’s matchup in Houston. In addition, Representative Tulsi Gabbard of Hawaii and Tom Steyer, a billionaire and former hedge fund investor, qualified to appear, the party said.

Candidates had until 11:59 p.m. on Tuesday to meet the Democratic National Committee’s requirements: amassing 130,000 individual donors and receiving 2 percent support in at least four qualifying polls.

The number of hopefuls sharing the stage is on the rise, but the overall field has grown smaller. Earlier this year, 20 candidates qualified for Democratic debates in Miami and Detroit. The party split those events into two nights, so that a maximum of 10 candidates appeared together.