The Democratic National Committee announced new qualification rules for the November debates Monday that could kick more candidates off the stage, as party leaders continue to push to shrink the field in the presidential nomination fight.

Sen. Amy Klobuchar (Minn.), former Housing and Urban Development secretary Julián Castro, and businessmen Andrew Yang and Tom Steyer are among those who could fail to qualify for the November debates if they do not improve their polling in the coming weeks.

Party Chair Tom Perez has been working to reduce the number of candidates at the debates since the first meeting in June, when he invited 20 to participate over two nights. The September debate had 10 qualifying candidates, and 11 have qualified for the next debate, which will be held Oct. 15 and possibly Oct. 16.

Under the new November rules, candidates will have to demonstrate they have 165,000 unique donors, an increase of 30,000 from the October qualification levels. They will also have to meet a new polling criteria, either by scoring 3 percent in at least four national or state polls approved by the party, or by receiving at least 5 percent in two approved single-state polls from Iowa, New Hampshire, South Carolina or Nevada.

The polls must have been released between Sept. 13 and one week before the date of the November debate, which has not yet been announced. The donors must also be geographically dispersed, with at least 600 coming from 20 individual states.

The higher thresholds effectively foreclose upon the hopes of rejoining the debate stage for many other candidates who failed to qualify for the September debates and remain unlikely to meet the October qualifications. Montana Gov. Steve Bullock, Sen. Michael F. Bennet (Colo.), former congressman John Delaney (Md.), Rep. Tim Ryan (Ohio) and author Marianne Williamson all appeared onstage in the summer events but have failed to qualify since then.

Rep. Tulsi Gabbard (Hawaii), who also dropped off the stage in September, has shown an ability to score 2 percent in some recent polls, and she needs only one more poll to qualify for next month’s debate. The rest of that group regularly poll at 1 percent or less. All have pledged, nonetheless, to continue their campaign.

Delaney, who has not polled over 1 percent in a party-approved survey in months, said he still sees a path to becoming president.

“The path is, the dynamics of the race change, which means a lot of people drop out, and people realize the top three polling candidates have vulnerabilities, which I think they do,” he said.

The Democratic National Committee plans to hold a total of 12 debates this nominating cycle, including monthly meetings for the rest of this year, and six more debates next year before the end of April.

Polling and donor thresholds for the debates have proved to be an unexpected and decisive factor in the first year of the presidential race. New York Mayor Bill de Blasio, Sen. Kirsten Gillibrand (N.Y.), former Colorado governor John Hickenlooper and Washington Gov. Jay Inslee have all ended their campaigns after it became clear that they would not meet the rising thresholds for the debates.

Castro has not received at least 3 percent in a party-sanctioned poll since late June, but his campaign said he had already met the donor threshold.

“We started this campaign with no list and no donor base, yet the grass-roots support is stepping up to say they want his voice on the debate stage month after month,” said Jennifer Fiore, a senior adviser to Castro.

Sen. Cory Booker, who has already notched 3 percent in two late September polls, announced this weekend that he would end his campaign if he did not raise an additional $1.7 million by the end of the month. His campaign manager, Addisu Demissie, tweeted after the new thresholds were announced that the campaign had not yet met the donor or polling threshold for November.

“Underscores the point of our call this weekend,” he wrote of the new qualifications. “We have to scale up this fall.”

Klobuchar hit 3 percent in an Iowa poll this weekend, her first since early August. Yang also regularly falls below the 3 percent threshold, though he notched 4 percent in a national September survey. Former congressman Beto O’Rourke (Tex.) has had more luck notching 3 percent in recent weeks, but he has only a single poll at that level since mid-September.

Steyer, who entered the race in July, has reached 3 percent in only one official poll, in early August.

Five other candidates appear likely to qualify for November, assuming they also have 165,000 donors. They are former vice president Joe Biden, Sen. Elizabeth Warren (Mass.), Sen. Bernie Sanders (I-Vt.), South Bend, Ind., Mayor Pete Buttigieg and Sen. Kamala D. Harris (Calif.).