Hofstra University’s debate stage will be set for only the two major-party candidates later this month, as the nonpartisan Commission on Presidential Debates announced Friday it has excluded Libertarian Party nominee Gary Johnson and Green Party candidate Jill Stein.

That makes the Sept. 26 debate the first head-to-head showdown between Democratic nominee Hillary Clinton and Republican candidate Donald Trump.

Under the commission’s rules, Johnson and Stein each needed to average at least 15 percent support in the most recent polls of five national polling organizations to be included.

Johnson had been vying for a spot and a Twitter campaign #LetGarydebate has been underway. But, according to the commission, he didn’t come close.

Polling numbers showed Clinton with 43 percent, Trump with 40.4 percent, Johnson with 8.4 percent and Stein with 3.2 percent.

The commission’s criteria for participation will be reapplied to all candidates before the second and third presidential debates, scheduled Oct. 9 at Washington University in St. Louis and Oct. 19 at the University of Nevada in Las Vegas.

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Johnson, in a post on his Facebook page Friday, wrote, “I would say I am surprised that the CPD has chosen to exclude me from the first debate, but I’m not. After all, the commission is a private organization created 30 years ago by the Republican and Democratic parties for the clear purpose of taking control of the only nationally televised presidential debates voters will see.

“Americans are tired of rigged systems, and the monopoly on debates created by the CPD is a prime and skillfully executed example,” he wrote.

Stein has been pushing to open the debates, organizing a petition drive on the issue.

On her website, she said, “Voters have a right to hear directly from their possible choices for the highest office in the land. These choices should reflect the diversity of American political opinion, and not be restricted to two candidates nominated by establishment parties awash in corporate donations and billionaire support.”

Clinton’s running mate, Tim Kaine, and Trump’s running mate, Mike Pence, qualified to participate in the the Oct. 4 vice-presidential debate at Longwood University in Farmville, Virginia, the commission announced on its website.

The 90-minute debate at Hofstra, to be held in the David S. Mack Sports and Exhibition Complex on the Hempstead campus, will be divided into six segments of about 15 minutes each on major topics that will be chosen by the lone moderator, “NBC Nightly News” anchor Lester Holt. The subjects will be announced at least one week ahead of time.

The commission, which oversees the event, said the moderator will begin each segment with a question. Each candidate will have two minutes to respond, and then may respond to each other. The remaining time in the segment will be devoted to “a deeper discussion of the topic,” the commission said.

Hofstra — Long Island’s largest private university — will become the first school to host presidential debates in three consecutive presidential election cycles.

In 2012, Democrat Barack Obama, running for re-election, and Republican Mitt Romney, the former Massachusetts governor, shared the stage. In 2008, Obama, then an Illinois senator, and Republican Sen. John McCain of Arizona faced off there.