WASHINGTON (AP) – South Carolina Republicans called on Fox News and the Republican National Committee on Wednesday to open their upcoming presidential debate to “all credible candidates.”

The lieutenant governor and House speaker were among 130 state Republicans listed in a letter charging that the plan to include only the top 10 candidates denies “all credible candidates an opportunity to have their voices heard on an equal basis at the beginning of the process.”

“Excluding candidates based on national polling at this point in the race rewards name recognition for those candidates who are celebrities, candidates who have run previously or candidates who have lots of money to purchase early national advertising,” the South Carolina Republicans wrote. “We urge you to let all of our candidates debate, let the early-voting states put the candidates through the ringer and let the voters decide.”

Republican leaders in New Hampshire and Iowa expressed similar concerns in recent days. The first nationally televised GOP debate is scheduled for Aug. 6.

National Republican officials and network executives have struggled to accommodate a 2016 Republican field expected to feature more than 15 high-profile candidates.

Fox News, the host of the first debate, plans to restrict it to the top 10 candidates based on polling averages from the five most recent national public opinion surveys. The network recently said candidates who do not qualify for the debate will be invited to participate in a forum to be aired on the afternoon of the debate.

A Fox News spokesman did not immediately respond to a request for comment Wednesday.

The second GOP presidential debate, hosted by CNN in September, will divide its event into two parts. One will feature the 10 highest-polling candidates while the other will feature the remaining candidates who register at least 1 percent in public polling.

South Carolina Lt. Gov. Henry McMaster said in an interview that networks should allow two debates that divide the field evenly.

“What we want to do is let everybody get on the stage – although certainly not altogether, that would be unwieldy and a waste of time – and break it out into two segments with every credible candidate on stage,” McMaster said in an interview with The Associated Press.