(CNN) Businessman Andrew Yang notched his fourth qualifying poll on Thursday, meaning he has now met the threshold to participate in the third Democratic primary debate in September.

In order to make the stage in September, candidates must receive 2% or more in at least 4 separate polls released between June 28 and August 28 and conducted by approved pollsters. Candidates must also receive donations from at least 130,000 individual donors distributed across multiple states.

Before coming in at 2% in Thursday's Monmouth University poll of likely Iowa caucusgoers, Yang claimed qualification on the basis of an NBC News/SurveyMonkey poll. But since one of his other three qualifying polls had also been a national poll sponsored by NBC, Yang needed one from another qualifying pollster to make the cut.

Nine candidates have now met the qualification for the September debate: former Vice President Joe Biden, New Jersey Sen. Cory Booker, Mayor Pete Buttigieg, California Sen. Kamala Harris, Minnesota Sen. Amy Klobuchar, former Rep. Beto O'Rourke, Vermont Sen. Bernie Sanders, Massachusetts Sen. Elizabeth Warren and Yang.

Eleven Democrats have said they received contributions from at least 130,000 individuals, coming from at least 400 unique donors in 20 or more states.

The Monmouth Poll is also billionaire Tom Steyer's third qualifying poll, making him and former Secretary of Housing and Urban Development Julián Castro one poll away from qualification on the polling side, though only Castro has reached his fundraising threshold. This is New York Sen. Kirsten Gillibrand's first qualifying poll.

Hawaii Rep. Tulsi Gabbard and former Colorado Gov. John Hickenlooper have one qualifying poll each, and Gabbard's campaign says she has met the fundraising threshold.

The Monmouth University poll found former Vice President Biden maintaining his lead in Iowa at 28% among likely Iowa Democratic caucusgoers, with Warren gaining momentum, up to 19% from 7% in their most recent April poll.

Harris follows with 11%, Sanders at 9%, Buttigieg at 8%, Klobuchar and Steyer at 3% each, and Gillibrand and Yang coming in at 2%. The rest of the tested candidates had 1% support or less.

new rule for the Iowa caucus creates virtual caucuses for those who can't participate in-person on caucus night, and preferences among those who participate virtually will only account for 10% of the delegates awarded on caucus night, no matter how many people participate in them. The Monmouth poll doesn't weight its results to match that 10% share of the delegate allocation, so likely virtual caucusgoers make up 20% of all likely caucusgoers in this poll.

That could benefit Biden. Biden performs better among likely virtual attendees than those who will likely attend in-person. According to Monmouth, Biden has 37% support among likely virtual attendees but stands at 26% among those likely to attend in person. Meanwhile, Warren has more support among those who will likely caucus in-person, 20% among that group vs. 10% among likely virtual attendees.

Health care is the reason for the election season in Iowa, with 55% of likely Democratic caucusgoers who cited it as one of the most important issues when deciding who to support for the nomination. Almost one-in-five said that their most important issues include climate change and global warming, followed by 15% who said the environment and pollution, 15% who said beating President Donald Trump, and 14% who said immigration.

Over half (56%) also said that they would like people to be allowed to either opt in to Medicare or keep their private coverage over getting rid of all private insurance (21%) or keeping it private for people under 65, but regulate the costs (13%). Only 4% of likely Democratic caucusgoers want to keep the system as is.

Almost three-in-10 Democratic caucusgoers in Iowa think that Biden is the candidate for president who comes the closest to their position on health care (28%), over Sanders (20%), and Warren (20%).

But when asked if they'd prefer a candidate who would have a hard time beating Trump but they agree with on most issues or someone who they didn't agree with but would be a stronger candidate against Trump, likely Democratic caucusgoers overwhelming said they would rather a strong candidate against the current president (72% to 20%).

The Monmouth University Poll was conducted by telephone from August 1 to 4, 2019 with 401 Iowa voters who are likely to attend the Democratic presidential caucuses in February 2020, out of 681 registered Democrats and unaffiliated voters who were contacted for the poll. The question results in this release have a margin of error of +/- 4.9 percentage points.