WASHINGTON — In one of Donald Trump's recent attacks on Democratic rival Hillary Clinton, he claimed she was “trying to rig” the televised presidential debate schedule.

Trump took to Twitter recently to protest the scheduled dates of the televised presidential debates this fall, accusing Clinton and the Democratic Party of manipulating the schedule to gain an advantage. In particular, he complained that two of the debates would conflict with NFL games.

The debate schedule, however, has been set for months. It's determined by a nonpartisan committee that dictates everything from the date and location of a debate to who will moderate.

The Commission on Presidential Debates has sponsored every general election presidential debate since 1988.

Though television networks will partner with party committees to broadcast primary campaign debates, general election debates are the commission's domain.

The commission said in a statement that it started working more than 18 months ago to consider the best dates for presidential debates, taking into account religious holidays, federal holidays and sporting events.

The commission said conflicts were unavoidable.

Here's how the commission produces presidential debates:

Who gets to host? The commission ultimately decides where debates are held, but different institutions can apply to be considered for selection. According to the commission, all but three of the debates it has organized have been held on college and university campuses.

The first debate this cycle was supposed to be hosted by Wright State University in Dayton, Ohio. The school later cited budget and security concerns for giving up the opportunity to host.

Complaints about the process. The commission has faced additional criticism leading up to this election cycle's debates.

In addition to Trump's complaints about the timing, the Green Party and Libertarian Party groups filed a lawsuit against the Federal Election Commission last summer. The parties, along with an advocacy group called Level the Playing Field, wanted the FEC to crack down on the commission. They said the commission's standards violate FEC rules that dictate debates must be staged in a nonpartisan manner.

Another controversy involves the requirement for a candidate to participate in a debate. The commission's 2016 rules mandate that a candidate must be polling at least 15 percent in an average of five national polls, using the most up-to-date polls from those five organizations.

The commission states the threshold balances the need to be inclusive to popular candidates while preventing the inclusion of candidates with minimal support from “jeopardizing the voter education purposes of the debates.”

According to the lawsuit brought before the FEC, it would be impossible for a candidate who does not run as a Democrat or Republican to meet the commission's 15 percent threshold.

What about the NFL? The league released its regular-season schedule in April.

The organization said it has no plans to change the dates of its games. It also said it did not send a letter to Trump — as Trump claimed — complaining about the debate conflicts.

jill.ornitz@latimes.com