There is growing anxiety among some GOP presidential campaigns that the rules for the next Republican presidential debate will unfairly eliminate some candidates.

If CNBC, the sponsor of the next debate on Oct. 28, decides to hold only one debate and limit the number of candidates who qualify, it would leave at least some of the 15 candidates without a stage.

“If we have learned anything from the campaign to date, we have learned that it is completely unpredictable and that conventional wisdom is anything but wise,” wrote Christian Ferry, manager of Sen. Lindsey Graham’s campaign.

The first two debate sponsors, Fox and CNN, each held two debates, with front-runners in a prime-time event and the rest of the candidates in a separate “undercard” event earlier in the night.

Ferry wrote a letter Monday to Reince Priebus, the chairman of the Republican National Committee, urging debate organizers to hold two debates and to randomly divide the candidates between them.

“This race is far from over and far from narrowing down,” Ferry wrote. “Let’s give voters the full picture and view of our party, not limit participation.”

Graham has complained all along that debate organizers were dividing the candidates based on national polls, rather than polling from the early primary states.

“The polling differences, nationally and in the early states, are so small or within the margin of error that using polls to determine who is in which place below the frontrunners is far from an accurate measure,” Ferry wrote.

Ferry also argued that the GOP would benefit from having Graham, Bobby Jindal, George Pataki and Rick Santorum on the same stage as the front-runners.

“These are not ‘also ran’ campaigns and the RNC should stop treating them as such,” he wrote.

Ferry said voters, not debate organizers, should narrow the field.

“The RNC should not punish smaller campaigns that have cautiously husbanded resources for the long haul,” he wrote.