Andrew Yang's presidential campaign accused the Democratic National Committee (DNC) of rejecting one of the two NBC polls that the tech entrepreneur had promoted as having qualified him for the September presidential debate, which left him short of making the stage for the crucial showdown.

In an email sent to campaigns by the DNC on Tuesday that was obtained by The Hill, the committee argued that a July 11 poll from NBC and The Wall Street Journal and a July 19 poll by NBC and SurveyMonkey, would only count as one poll because they were conducted by the same sponsor - NBC.

The email did not refer to Yang specifically, but it came after the Yang campaign had announced in a media statement that it had qualified for the fall debate.

In a separate tweet, Yang cited 4 different polls where the candidate had at least 2 percent support, including listing the 2 NBC polls separately, while touting his qualification for the fall debate.

The DNC, however, emailed campaigns to inform them that only one of the NBC polls listed by the Yang tweet could be submitted for its qualification criteria.

"Candidates may only count one NBC-sponsored national poll released during the current qualification period," DNC senior adviser Mary Beth Cahill said in the email, which was also sent to the Yang campaign.

"A particularly important rule in our debate framework is the requirement that candidates' initial qualifying poll be conducted by different sponsors, or if by the same sponsor, in different geographies," she wrote. "The intent of this rule is to avoid scenarios in which a single poll sponsor or media outlet is responsible for qualifying a candidate through multiple sets of results in the same geography."

To qualify for the September debates, candidates must get 2 percent support in at least four polls and win 130,000 donors. Yang has met the donor threshold.

Only seven candidates have qualified for the September debate so far, as the thresholds for making the stage are higher than those for the party's earlier debates.

DNC spokeswoman Adrienne Watson confirmed that the DNC sent the email to campaigns, including Yang's, and referred The Hill to the rules sent out earlier.

The Yang campaign pushed back against the DNC, however.

"By the DNC's own rules, the Wall Street Journal, NBC News, Fox News, and Quinnipiac are all approved organizations, and thus Andrew Yang has qualified for the fall debates. We disagree with the DNC decision and are disappointed with the ruling," Yang's campaign manger Zach Graumann said in a statement to The Hill that was later sent out publicly.

"It is frustrating to see the rules be changed mid-game, but our campaign has overcome every obstacle placed in our path, and we will continue to upset the establishment well into 2020," the statement added.

Yang is a former tech executive who launched what has been seen as a long-shot bid for the White House. His campaign has gained notoriety for making a $1,000 a month universal basic income its signature issue. He is scheduled to appear in Wednesday's DNC debate.

The DNC's polling deadline for the upcoming debates is Aug. 28, so Yang could still qualify if he finds sufficient support in one more approved poll.

Updated at 2:51 p.m.