The first Republican presidential debate will be on Thursday, August 6. But the controversial question of who'll make it onstage still hasn't been answered.

Debate host Fox News can't reasonably fit the 16 GOP candidates in the race on the stage and give them each enough time for much more than an opening and closing remark. So Fox is limiting the debate to only the top 10 contenders in national polls — using criteria that have ruffled some feathers and opened the network to criticisms over a lack of transparency in its methods.

As a result, many candidates have been caught in a bind. About half — eight of the 16 in the field — have been polling below 5 percent, so they've all been desperate for a chance to impress GOP voters and boost their standing. The debate could be that chance — but if they don't manage to do better in national polls, they won't even be let in. And it's quite hard to get the media attention needed to make those national poll gains, given the saturation coverage of Donald Trump.

Indeed, some even fear that the debate selection process will change the very way the primary campaigns have traditionally worked — effectively winnowing the field months before early state voting begins.

What determines which candidates make the cut for the debate?

The short answer is that Fox News will pick the 10 GOP candidates doing best in an average of national polls.

Specifically, the network has said it will look at the five most recently conducted national polls from "major, nationally recognized organizations that use standard methodological techniques" up to 5 pm Eastern time on Tuesday, August 4 (tomorrow, which is two days before the debate).

But there are some specifics that Fox News has been much more vague about, as Harry Enten has been covering at FiveThirtyEight. Particularly:

Which polls will count? When Fox News says it wants polls using "standard methodological techniques," what does it mean? Will the network recognize only polls that use live interviewers to speak to respondents, or will it count robo-polls or internet polls too? And which specific organizations does the network view as "major" and "nationally recognized?" (On Monday afternoon, a source finally told Gabriel Sherman of New York Magazine that the polls would have to use live interviewers, but the network still hasn't confirmed that publicly. At least three new live interview polls will be released Tuesday.) How will rounding be handled? Since several candidates are polling in the low single digits, decimal points could make a crucial difference, in both individual polls and the averages. If a poll finds a candidate at 2.5 percent, for instance, it's not clear whether, when Fox News enters it into its averages, it will round that up to 3, down to 2, or keep it where it is. Then there's the possible rounding of the averages themselves — will an average of 2.8 points beat 2.7, or will both be rounded up to 3, creating a tie? And then what happens if there's a tie? If, say, two candidates end up tied for 10th place, will Fox News include them both? Or will it use a tiebreaker of some kind to limit the candidates on stage to 10?

By contrast, CNN, which is hosting the second GOP debate, has been extremely transparent about about these questions. It will average all live interview polls conducted by 14 specific organizations released between July 16 and September 10. It won't round the polling averages, and it will use two tiebreakers.

Fox News's opacity, in comparison, could give the network some flexibility to choose which minor contenders make the cut. Unless the network publicly announces more specifics in advance, it could wait for the polls to come in and then see which criteria produce the result it likes best.

Who's likely to qualify for the debates?

While there's still one more day in which things could change, recent national polls suggest that eight of the 10 debate slots will be filled by the candidates above, and that the other two will be up for grabs.

In the current RealClearPolitics average of polls, Trump, Bush, and Walker are the clear leaders, with each getting above 10 percent. Absent a quick collapse, all three are assured a ticket in.

Then there are five more candidates clustered around the 5 to 7 percent level. They are Marco Rubio, Ben Carson, Rand Paul, Mike Huckabee, and Ted Cruz. None of them are polling well, but there's a gap of a couple points between them and the next batch of contenders.

That would leave two more slots for the eight GOP candidates doing worst in the polls to fight over.

Wait, so Donald Trump is really going to be in the debate?

Trump has led all the recent national polls, so barring some shocking movement in the new ones released Tuesday, he won't just be on the stage, he'll be center stage (where poll leaders are usually positioned).

The prospect has caused Republican elites heartburn — and indeed, the New York Times's Maggie Haberman and Jonathan Martin reported that GOP donors and operatives were recently scheming about how to keep Trump out. Their problem, though, was that party elites have no real power to make this happen — the media organizations hosting the debates get to decide who qualifies. And to them, Trump is not only the poll leader, but also ratings gold.

So, the Times reported, party officials brainstormed about how to force the networks' hands. Some thought that if they could convince the other major candidates to agree not to participate in any debate with Trump — using the "pretext" that Trump's potential third-party run makes him unsuitable for a GOP debate — the networks would cave and find a reason to exclude the mogul. But the other candidates showed no interest in voluntarily withdrawing from a debate that could be crucial in boosting their profiles.

Who's in serious danger of failing to make the cut?

The eight candidates above are all polling quite low — usually between 0 and 3 percent. And only two of them will likely make it into the debate.

This isn't a bunch of random kooks. John Kasich, Chris Christie, and Bobby Jindal are sitting governors — with Kasich governing the crucial presidential swing state of Ohio, which also happens to be where this debate is located. Lindsey Graham is a sitting senator and a leading GOP voice on foreign policy. Rick Perry and Rick Santorum ran in 2012 — the former led polls briefly, and the latter won the Iowa caucuses. Carly Fiorina was a Fortune 500 CEO and is the only female candidate in the GOP field. George Pataki ... has been out of politics for a while, but did govern New York for 12 years. It's natural for utterly unknown candidates to be excluded from the debates, but by traditional metrics, this is quite a qualified bunch.

Currently it looks like Chris Christie, John Kasich, and Rick Perry will be battling for those two remaining slots. Yet relying on national polls to exclude so many candidates feels random and unfair to many — particularly because poll sampling error and pure random chance could be major factors in determining which two get in.

As the Upshot's Kevin Quealy and Amanda Cox explained, polls of GOP primary voters tend to have sample sizes of only a few hundred, so the responses of just a couple people who happen to be in the sample could elevate one of the bottom candidates above the others. "Methodologically, they might as well be drawing straws," Steven Yaccino of Bloomberg Politics wrote.

There's a small consolation for the candidates who don't make it — they can participate in a Fox News forum held earlier in the day. But far fewer people are expected to watch this "loser's bracket" forum at 5 pm on a workday, compared with the primetime main event.

The candidates are trying to adapt to the new system

Candidates who fail to make the debate aren't necessarily at the end of the road. They could focus on a more traditional strategy of campaigning hard in Iowa or New Hampshire — a strategy that helped Mike Huckabee and Rick Santorum come out of nowhere to win the Iowa caucuses in 2008 and 2012, respectively.

Yet if donors and potential donors view not qualifying for the debates as a serious failure, these candidates' money and support could dry up — and they could be forced to drop out of the race as a result.

Indeed, some observers, especially those in states with early primaries, like New Hampshire, fear that limiting entrance to the debates could prematurely winnow the field months before anyone votes.

It's a fear that's somewhat overstated — 10 candidates is still quite a lot to choose from, and some presidential candidates usually drop out well before the voting starts. But it is true that national polls have never been so important before — and that breaking through in them is expensive and difficult.

The national media has little interest spending much time covering ordinary campaign events, where the candidate recites his or her stump speech and takes positions similar to everyone else in his or her party. Instead, controversy gets airtime, as in the case of Trump. It's possible to go around the media and try to drive up a candidate's poll numbers with a national ad campaign, but that's quite expensive compared with early state spending.

So some candidates are already changing strategy to adapt to these new imperatives, desperately seeking to insert themselves into the national conversation somehow, as Vox's Jon Allen has written. Rick Perry, currently in 11th in the RealClearPolitics average, has seemed particularly desperate to qualify, and is trying to get more attention from the national media by capitalizing on the Trump phenomenon. He's picked a fight with the billionaire and even gave a speech in which he announced the "cancer" of what he called "Trumpism."

Meanwhile, Perry's Super PAC has been running national ads — a very unusual move, since primary candidates usually save their advertising money for early states. "We want to see him on that debate stage," Super PAC adviser Austin Barbour told the New York Times. Perry's operation can afford this — his Super PACs have raised $16 million so far, much of it from just a few donors. Chris Christie and his Super PAC have also been advertising nationally, on Fox News, leading some to gripe that the network is profiting from its restrictive debate criteria. But the cost of national ads would likely be prohibitive to the minor candidates who aren't so well-funded.

So far, Perry's gambit hasn't succeeded in boosting his numbers. What's already clear, though, is that 10 or so candidates will win big by merely getting into the debates — and the rest will have some explaining to do.