LOS ANGELES — The Democratic National Committee will again increase the qualification standards for its next debate in January, requiring candidates to receive at least 5 percent support in four qualifying polls, or 7 percent in two early-state polls, making it likely that the field of candidates will be winnowed further for the event.
The announcement on Friday from Tom Perez, the D.N.C. chairman, came despite intense public and private lobbying from Senator Cory Booker of New Jersey and his allies to lower the barrier to participate in the party’s debates, a cause that gained momentum after just one person of color, entrepreneur Andrew Yang, qualified for Thursday’s debate in Los Angeles.
Five candidates — former Vice President Joseph R. Biden Jr., Mayor Pete Buttigieg of South Bend, Ind., Senator Amy Klobuchar of Minnesota, Senator Bernie Sanders of Vermont and Senator Elizabeth Warren of Massachusetts — have already met the 5 percent threshold and the donor threshold of at least 225,000 individual donors, meaning they will receive invitations to the next debate, scheduled for Jan. 14 in Des Moines.
Mayor Michael R. Bloomberg of New York has also met the polling standard but will be thwarted by the donor requirement, unless he changes his stance against accepting contributions from others.
But two candidates who were on Thursday’s debate stage in Los Angeles — the businessman Tom Steyer and Mr. Yang — will have work to do in order to qualify for January. Mr. Steyer has met the polling mark twice during the window set by the D.N.C.; Mr. Yang has reached 5 percent only once in that period.
“Whatever qualifications they set, you know that this guy is going to be there,” Mr. Yang said Thursday while touring a pop-up store selling campaign merchandise in the Fairfax section of Los Angeles. “The Yang Gang cannot be stopped. We are growing when other campaigns are shrinking and we are going to be there through the spring as the voting gets underway.”
Short of a dramatic turnaround in his fortunes, the 5 percent threshold will doom Mr. Booker’s chances of returning to the debate stage. He has not reached 5 percent in a qualifying poll since March. The former housing secretary Julián Castro, the only Latino candidate in the race, has never reached 5 percent.
The January debate, scheduled to take place at Drake University, could be moved or postponed if President Trump’s impeachment trial in the Senate is taking place in mid-January. It remains unknown when the trial will begin or how long it will last.
Three more debates are planned for February — one each in New Hampshire, Nevada and South Carolina.
Mr. Booker on Saturday organized eight other Democratic presidential candidates to sign a letter to Mr. Perez asking that debate thresholds be lowered in a way that would allow him and Mr. Castro to participate in the January and February debates.