Sen. Bernie SandersBernard (Bernie) SandersThe Memo: Tide turns on Kavanaugh Election Countdown: Trump confident about midterms in Hill.TV interview | Kavanaugh controversy tests candidates | Sanders, Warren ponder if both can run | Super PACs spending big | Two states open general election voting Friday | Latest Senate polls READ: President Trump’s exclusive interview with Hill.TV MORE (I-Vt.) on Sunday said the percentage of popular support candidates need to participate in the presidential debates should "probably" be lower than what it is now.

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"Probably too high," Sanders, who challenged Hillary ClintonHillary Diane Rodham ClintonHillicon Valley: Trump's exclusive interview with Hill.TV | Trump, intel officials clash over Russia docs | EU investigating Amazon | Military gets new cyber authority | Flynn sentencing sparks new questions about Mueller probe READ: President Trump’s exclusive interview with Hill.TV Keeping up with Michael Avenatti MORE for the Democratic nomination, said on NBC's "Meet the Press" when asked whether he thinks that threshold is fair.

Libertarian nominee Gary JohnsonGary Earl JohnsonRand Paul endorses Gary Johnson's Senate bid The Hill's Morning Report — Trump casts energy, land policies as gifts to red-state voters Poll finds Libertarian Senate candidate running ahead of GOP in New Mexico MORE and Green Party nominee Jill Stein have been making a case for why they should be allowed to take part in the presidential debates.

To participate, a candidate needs to hit an average of 15 percent in polls conducted by ABC/Washington Post, CBS/New York Times, CNN/Opinion Research Corporation, Fox News and NBC/Wall Street Journal.

Stein said Sunday morning that the American people have a right to vote and to know for whom they can vote. 

A recent poll by Morning Consult showed that a majority of voters say Johnson should take part in the presidential debates. Nearly 50 percent say the same of Stein.

But neither candidate appears to be polling high enough at this point to participate in the presidential debates.

According to the RealClearPolitics average of polls, Johnson is polling at 7.8 percent and Stein at 3.1 percent.