Republican debate participants (top row L-R) Donald Trump, Jeb Bush, Scott Walker, Mike Huckabee, Ben Carson, (bottow row L-R) Ted Cruz, Marco Rubio, Rand Paul, Chris Christie and John Kasich. (Staff/Reuters)

Ten of the “leading” Republican candidates gather Thursday night for the first presidential primary debate.  Of course, they’re “leading” only if you ignore the sampling error in polls. But never mind.

So, about the 497 things.  I was kidding. There are only four:

1) Debates can move the polls.

This is possible in the presidential general election, and it’s even more possible in the primary campaign, when the candidates are less familiar and lots of people haven’t made up in their mind. There were two good examples of this during the 2012 campaign. (And maybe a third — see Kyle Kondik and Geoffrey Skelley on Rick Perry.)

The first example involved Herman Cain. In the fall of 2011, Cain’s poll numbers increased about 10 points in the week after the Oct. 11 debate. You may recall that he was promoting his “9-9-9 tax plan,” perhaps?  (If not, good for you.)

The second example involved Newt Gingrich and was more consequential. There were two key debates here, both held in South Carolina right before its primary on Jan. 21, 2012.

In the first debate, Gingrich drew attention for his response to debate moderator Juan Williams, who questioned Gingrich’s assertions that President Obama was the “food stamp president” and that poor children would learn valuable lessons from working as janitors.  In the second debate, Gingrich responded angrily to the moderator, John King, for bringing up Gingrich’s ex-wife’s claim that he had asked for an open marriage. CNN called Gingrich’s performance a “show stopper.”

After these two debates, Gingrich’s share of news coverage increased nearly four-fold, and his poll numbers shot up, too. Arguably, this gave him the momentum he needed to win the South Carolina primary.

But note the “can” in the phrase “can move the polls.” I’ve mentioned only three debates out of the 20 Republican debates in 2011-2012. Most of the debates, as David Byler documents, didn’t produce this kind of movement.  As Byler notes, lots of debates didn’t produce memorable moments, or introduce new information about the candidates.

2) Debates rarely determine the election’s outcome.

You may have noticed that neither Cain nor Gingrich became the Republican nominee.  That’s because debates rarely propel a candidate to victory in the actual election. That’s true in the general election, as well, as I wrote in 2012. Mitt Romney’s perceived victory in the first debate — and subsequent loss on Election Day — is a good illustration.

A debate performance that’s judged favorably can produce the equivalent of a sugar high: a few news cycles of positive coverage and a polling surge. If that surge is well-timed, you can maybe win the next primary, as Gingrich did.

But the high almost always wears off. A good debate performance isn’t real nourishment for a campaign. A candidate needs support among party leaders, for one. It’s these fundamentals of the election that matter most. A few good one-liners from the podium won’t suffice.

[Why you should ignore the Republican presidential primary polls]

3) The debate offers another candidate a real chance to be “discovered” — and thereby knock Donald Trump off the top of  the polls.

As I’ve argued, Donald Trump’s surge in the polls was catalyzed by news attention after he announced his candidacy. Lynn Vavreck and I documented this pattern happening in 2011-2012, as well — including to Cain and Perry. And, as we also documented, a polling surge can then provide justification for additional news coverage. In other words, that initial spate of news attention plants the seeds for its continuation.

What brings the surge to a close? One ingredient is the scrutiny of the news media. But another is the discovery of a different candidate.

Let’s go back to Cain in 2011. His surge in the polls didn’t start with that October debate. It started two weeks before, when he won the Florida straw poll on Sept. 24.

This was consequential not only for Cain, but for Perry. The media’s “discovery” of Cain at this point came at Perry’s expense. Perry’s share of news coverage fell as Cain’s rose. And it didn’t help that several media outlets framed Cain as “upsetting” Perry in the straw poll. This was arguably the beginning of the end of Perry’s campaign, and it came well before the Texas governor’s “oops” moment in a later debate.

This brings us to Trump. He has received some scrutiny in the news media (for example, here, here and here). But his share of news coverage has increased, if anything — and alongside it, his poll numbers, too.

[Why is Trump surging? Blame the media.]

So, scrutiny may not be enough. For Trump to be dislodged as the candidate with the most news coverage and highest poll numbers, another candidate may need to be “discovered” — just as Cain was after the Florida straw poll.

As the Cain example shows, it doesn’t even matter if the event that leads to the discovery is meaningful. The Florida straw poll was a nonbinding survey of the approximately 2,700 people who showed up to a GOP meeting in Orlando.

Thursday’s debate is thus a key opening for the other Republican candidates. If someone is discovered, or discovered anew, it may not catapult them to the nomination. But it may knock Trump off the top of the polls.

4) The media’s reaction to the debate may matter more than the debate itself.

Most people won’t watch the debate. Heck, most Republican primary voters won’t watch the debate. So, how do people form impressions of who wins a debate? The news media plays a crucial role.

In 2012, I discussed a noteworthy experiment by Kim Fridkin and other scholars at Arizona State University. During the 2004 campaign, they showed people some footage of the third presidential debate; or the debate, plus 20 minutes of post-debate commentary on NBC; or the debate, plus 20 minutes’ time to read commentary on CNN.com.

Who won that debate, George W. Bush or John Kerry?  It depended on which news coverage people saw. Those watching the debate tended to think that Kerry had won, as did those who read analysis on CNN.  But those who watched the NBC postmortem had the opposite impression. Fridkin and colleagues write:

Our findings suggest that voters’ attitudes are influenced by the arguments presented directly by the candidates during the debate as well as by the media’s instant analyses of the candidates’ debate performances…the impact of the candidates’ messages was often altered by the media’s instant analyses.

That supports scholarship showing that the news media does a lot of interpretive work for us — framing events in particular ways, telling us how to interpret these events, and so on. Those judgments are sometimes explicit and sometimes phrased in passive voice constructions (“Senator Smith was widely seen as victorious”) or sourced to, well, others in the news media (“Many commentators saw Senator Smith as victorious”).

So even if you don’t watch the debate, you may be able to tell which candidate, if any, will benefit — and whether that candidate is someone other than Trump. Just read the news on Friday.