DENVER — The commission that oversees presidential debates has invited only Hillary Clinton and Donald Trump to the first presidential debate. It excluded two third-party candidates who had hoped the event could help them talk directly to an electorate unhappy with the two front-runners.

The Commission on Presidential Debates said in a statement Friday that Libertarian nominee Gary Johnson and Green Party nominee Jill Stein were polling too low to qualify for the Sept. 26 event. The commission since 2000 has invited only candidates polling at 15 percent or above in an average of five polls. Johnson was at 8.4 percent and Stein at 3.2 percent.

Johnson, a former New Mexico governor and ex-Republican who is running with former Massachusetts governor Bill Weld, has been pushing aggressively to get into the debate. He and Stein could still qualify for the two remaining ones in October if their poll numbers hit 15 percent, but that will be challenging without the national exposure of the debate.

In a statement, Johnson slammed the commission as a tool of the Democratic and Republican parties and vowed to make the October contests. “The CPD may scoff at a ticket that enjoys ‘only’ 9 or 10% in their hand-selected polls, but even 9% represents 13 million voters, more than the total population of Ohio and most other states,” Johnson said.