For GOP presidential candidates, winning the right to participate in the first debate on Fox News next month means they'll have to be ranked as one of the top 10 contenders, but that ranking may well depend on which polls are used.

A Fox press release from May says the leading 10 candidates, based on an average of the five most recent national polls, will be able to debate. The polls "must be conducted by major, nationally recognized organizations that use standard methodological techniques," Fox said.

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But there are more than five national polls and that means the 10 candidates who make it to the stage will depend on which five polls Fox uses, and how those polls treat the candidates. Fox did not return a request for comment on how it will determine which polls it will use.

Different polls sample different people, and that can produce different results that either benefit or work against a candidate's odds to secure a coveted spot on the stage.

For example, out of five of the latest polls, two of them would put former Hewlett-Packard CEO Carly Fiorina, a longshot for the GOP nomination, into the top 10 and access to the debate.

A Fox News poll released on June 24 had Fiorina polling at 3 percent, which was ninth place among the 16 declared or likely Republican presidential candidates. That poll surveyed "likely Republican voters."

Likewise, an NBC/Wall Street Journal poll from June 21, which surveyed "Republican primary voters" (but not necessarily likely voters) had her at 2 percent, or 10th place among the candidates.

Both the Fox and NBC/Wall Street Journal poll are favorable for Fiorina, whose campaign would likely benefit from the free exposure and legitimacy a nationally-televised primetime debate provides. But in other polls, Fiorina does not have the advantage.

A Washington Post/ABC News poll released June 3 showed Fiorina polling in 12th place, thus disqualifying her from the debate stage. That one included independent voters who are "Republican-leaning."

If enough of the wrong polls show up, it could spell doom for certain candidates who are hanging on at the tail end of the pack, and who desperately want to be seen as part of the top 10 group.

Fiorina's campaign is aware of the discrepancies. "Not all national polls are created equally," said a spokeswoman. "Carly is No. 9 in the Fox poll for a reason."

Another issue is many Republican Party insiders are fretting over is real estate mogul-turned reality TV star Donald Trump's likely inclusion in the debates. Most national polls that include him as a candidate – he officially said he's running in June — currently show him within the top 10 spots.

But a Monmouth University poll from June 15 of Republican and "Republican-leaning" voters doesn't. He's tied with Fiorina and South Carolina Sen. Lindsey Graham in 11th place.

Fox's debate sorting method caused controversy, with leading Republican activists in New Hampshire calling on the network to entirely re-format the debate.

Fox, however, hasn't budged. Michael Clemente, the network's executive vice president of news and editorial, said in June that the declared candidates who don't qualify for the debate will instead be given an opportunity to participate in a forum earlier in the day.

Both the forum and the debate are set to take place in Cleveland, Ohio, on Aug. 6.