Like the best reality TV shows, it has all the elements.

There’s the unscripted dialogue, frequent verbal clashes and the occasional mortifying moment to give viewers something to talk about the next day. There’s the diverse and occasionally wacky cast of characters — the would-be front-runner (Mitt Romney), the plain-talkin’ challenger (Rick Perry), the come-from-behind guy (Newt Gingrich), the feisty grandpa (Ron Paul), and the plucky female contender (Michele Bachmann). There are underdog figures, too (Rick Santorum and Jon Huntsman), who never seem to get the same amount of airtime as the bigger stars.

The Republican primary debates — 15 full-fledged ones so far, and another Thursday night on Fox News Channel — have turned into one of the fall television season’s surprise hits. A record 7.6 million people tuned in Saturday night, barely three weeks before the first caucus in Iowa. The five most popular debates in recent weeks have attracted an average of 5.6 million viewers, a figure that would rank them as the most popular series on cable after pro-football games, and just behind middle-ranked sitcoms such as “Parks and Recreation” on the broadcast networks.

Surely, viewers of all political persuasions are drawn by the consequential nature of the discussion — taxes, the economic crisis, stances on foreign policy — and by a desire to learn who might be best qualified to challenge for the presidency next fall. But this year’s debate-a-thon, which will surely surpass the record of 21 held by Republicans during the 2007-08 cycle, has some bonus features as well.

“There’s hype, there’s drama, there’s uncertainty,” said Mitchell McKinney, a communications professor at the University of Missouri who specializes in political debates. “The debates have become like a reality show, like the next version of ‘Survivor.’ ”

Each of the debates has produced a newsworthy (or at least sound-bite-worthy) moment or two. In Saturday’s debate, it was Romney offering to bet Perry $10,000 over a disagreement about a passage from Romney’s book. Perry had his own mortifying “oops” moment last month when he couldn’t remember the name of a third federal agency he would dismantle if elected. Herman Cain, now gone, is likely to be most remembered for repeatedly invoking his “9-9-9” plan during the debates. Or possibly for repeatedly calling CNN moderator Wolf Blitzer “Blitz” during one of his answers.

Even audience reactions have been noteworthy, such as the booing that followed a gay soldier’s question in September about whether the candidates would reinstate the military’s “don’t ask, don’t tell” policy.

All of it seems to matter; the debates have been critical in shifting public perceptions of the candidates, leading to an unsettled and suspenseful race — which, of course, amplifies the stakes for the next debate.

Perry’s candidacy ran into big trouble with his debate brain freeze. Gingrich’s rise from near-dead to the top of the polls in recent weeks is largely credited to his debate performances. The fallout from Romney’s proposed bet with Perry last week still isn’t clear, but it couldn’t have helped; Huntsman and Bachmann’s campaigns jumped on it as a sign that Romney is out of touch with average Americans, as did the Democratic National Committee.

“There’s a general uncertainty among Republican voters about who they should turn to to be their messenger and what that message should be,” McKinney said. “There’s lots of volatility here. That’s part of the drama, too.”

It helps, too, that the sponsors of the debates are television networks, and particularly the cable news networks. Under their aegis, the debates have become full-fledged TV productions, with audience-building promotions and discussion shows before the debate and “wrap-up” shows afterward that mimic the hoopla surrounding a big football game.

The debates tend to be loss-leaders for the networks, typically costing upwards of $1 million to produce. That investment can’t be recouped via the limited number of commercials that air during each debate. But sponsoring a debate helps promote the network’s brand among viewers for the long campaign to follow, said Sam Feist, CNN’s Washington bureau chief and the executive producer of the four debates it has sponsored so far.

“The debates have been fascinating to watch this year,” Feist said. “They have been interesting and important at the same time. There are lots of [programs] that are important but not interesting, and some that are interesting but not important. These are both. The country is facing significant challenges, and there are viewers and voters who are trying to decide which of the candidates to vote for. You have independents and Democrats watching, too.”

Feist argues that the debates are a better way than campaign ads for voters to get information about the candidates. The largely unscripted statements and exchanges reveal more about the candidates than 30-second commercials, he says.

The only people who seem less than pleased about the debates are those running TV stations that count on those ads every four years.

The number of debates, and the broad national exposure they’ve provided, have diminished the need for TV commercials in the early primary states, said Ken Goldstein, who heads Campaign Media Advertising Group (CMAG), an Arlington company that tracks political ad spending.

In fact, ad spending in the two early voting states is way down this year, even accounting for the fact that only one party is contesting the nomination this year compared with two in 2007. The Republican candidates and political action committees have spent $3.3 million on TV ads in Des Moines, Cedar Rapids and other Iowa cities so far this year, according to CMAG, vs. $27.4 million at this point during the last campaign.

In New Hampshire, the figure this year is $1.3 million compared with $17.2 million four years ago.

Some candidates haven’t shown up on the air at all. As of Tuesday, Gingrich had yet to run a spot in New Hampshire. Former Minnesota governor Tim Pawlenty spent more on TV ads in Iowa before dropping out of the race in August than Santorum, Huntsman or Bachmann have through mid-December, according to CMAG.

Dale Woods, president of WHO, the NBC affiliate in Des Moines, said his station saw a slight jump in political ad sales after Saturday’s debate. But with only three weeks before the Iowa caucus, that’s a late start. In particular, Woods says, Gingrich and Romney have been slow to take to the local airwaves. “Romney was much more aggressive last time,” said Woods. “But that could be because he’s concentrating on New Hampshire,” where his prospects are much stronger than in Iowa.

This suggests an underappreciated aspect of the debates: that they keep candidates with limited bankrolls and the lagging poll numbers in the race longer. Relieved of the necessity to keep pace in the advertising arms race, candidates such as Santorum, Bachmann and Huntsman can hang around longer.

Just ask Gingrich. Six months ago, his campaign broke and in disarray, he seemed poised to disappear. Today, he’s still on the island. And he may be there next fall, too.