On Sept. 16, the commission said that Gary Johnson would not be allowed to participate in the first debate on Sept. 26.

Johnson is currently polling at 8%. He is below the 15% threshold required to participate in the debates.

Mr. Johnson has maintained an average of about 10 percentage points since June, when pollsters started including him in surveys.

The commission also requires a candidate to be on the ballot in enough states to have a mathematical chance of winning 270 electoral votes. Mr. Johnson is well past that threshold, according to the Libertarian Party’s website. The Green Party candidate, Jill Stein, also has passed the state ballot threshold and is currently polling at around 3 percent.

H. Ross Perot, who ran as an independent candidate in 1992, was able to participate in debates as part of an agreement with the campaigns of George H.W. Bush and Bill Clinton. Mr. Perot was polling at 10 percent to 20 percent in the fall of 1992 and received nearly 19 percent of the nationwide vote.