Republican presidential candidates take the stage for the first Republican presidential debate at the Quicken Loans Arena Thursday, Aug. 6, 2015, in Cleveland. (John Minchillo/AP)

The rapidly shifting dynamic of the 2016 presidential campaign will probably turn the second Republican debate into a far more contentious event than the first.

The month since the first debate in early August has seen the contest take a rougher direction, as Donald Trump continues to dominate the race and confound his rivals by skating over pitfalls that would be expected to doom any of them.

So they are no longer counting on Trump to be the architect of his own demise. Former Florida governor Jeb Bush has begun attacking Trump directly, while others, such as Gov. Scott Walker of Wisconsin, have sought to appear much more forceful so as not to be totally overshadowed by the tough-talking real estate mogul and reality TV star.

Long shots, such as Sen. Rand Paul of Kentucky and Gov. Chris Christie of New Jersey, have indicated that they plan to be more assertive in the second debate. And, unlike the first go-round, this one is likely to include former Hewlett-Packard chief executive Carly Fiorina, who has shown a willingness and ability to hit hard.

The newfound aggression, however, has not improved the standing of many candidates, leaving them eager for a breakout moment at the Sept. 16 event at the Ronald Reagan Presidential Library in Simi Valley, Calif.

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“A panic has set in on a number of campaigns. I’m expecting this next debate could more resemble roller derby than a debate,” said John Weaver, an adviser to the campaign of Gov. John Kasich of Ohio, one of the few of the GOP hopefuls to experience a bit of a bump since the first debate.

Newt Gingrich, who distinguished himself as a scrappy debater during his 2012 bid for the presidency, said the imperative to stop Trump’s momentum has grown ever more urgent for the rest of the field.

“Somebody is going to make a run at Trump,” Gingrich said. “I assume it will be Jeb Bush,” whose status as a presumed favorite has been dented the most by Trump.

Going after Trump potentially comes at the cost of a candidate being thrown off his or her own messages at a high-profile moment and blowing an opportunity to emerge as the most attractive alternative to the blustery billionaire. And the one thing that anyone who attacks Trump can count upon is a gale-force response.

“As best as possible, when there is chaos all around you, you still have to focus on the things that make you unique,” Weaver said.

Conservative radio host Hugh Hewitt, who will be one of the questioners, predicted: “Debate #1 was touch gloves with each other. This one will be a lot sparkier, but I don’t think it will be all pile up on Donald Trump.”

The debate is almost certain to be one of the most watched moments of the campaign so far. The first showdown drew more than 24 million viewers to sponsor Fox News, a record for a non-sports cable telecast. CNN, which is broadcasting this one, is widely reported to be asking advertisers to pay as much as $200,000 for a 30-second spot, which is 40 times its normal rate.

Bush’s jabs at Trump on the campaign trail and in social media represent a shift for a candidate who had vowed to stay positive. But it is a move that Bush has decided is necessary — not only at the next debate but continuing into the fall.

But in doing so, he could create an opening for someone else.

“You want to be like Kasich and [Florida Sen. Marco] Rubio — the nice, pleasant guys who are appealing to the country while the others are engaging in a mud fight,” Gingrich said.

Indeed, one of the overlooked story lines of the first debate was how a graceful and upbeat performance sparked the quiet rise of retired neurosurgeon Ben Carson, who in the latest Des Moines Register poll is running second in Iowa, just five percentage points behind Trump.

The poll of likely Republican caucus-goers in the state that will hold the first contest of the 2016 primary season also showed Carson with the highest favorability of the 17 GOP candidates, with 79 percent viewing him positively.

Fiorina, meanwhile, was able to capi­tal­ize on a skillful performance in the so-called “undercard” debate of lower-polling candidates that preceded the main event in Cleveland, boosting her numbers so quickly that CNN rewrote the rules for qualifying so that she is expected to join the leading candidates at the Reagan Library event. The network will announce Thursday which candidates make the cut, which will be determined by looking at polling since Aug. 7.

Fiorina and Trump, both running as outsiders from the business world, have taken a number of shots at each other.

He has branded her a failure, citing her firing from Hewlett-Packard and the fact that she got trounced in 2010 when she tried to unseat Sen. Barbara Boxer (D-Calif.). Fiorina has criticized Trump for his intensely personal attacks on Fox News debate moderator Megyn Kelly, among other things.

In an interview with Fox News Radio’s Brian Kilmeade, Fiorina said the other candidates should be focusing more of their fire on the likely Democratic nominee, former secretary of state Hillary Rodham Clinton, because “in the end, we need a nominee who can beat whoever the Democrats put up.”

But “if it’s important to draw contrast between myself and Donald Trump, I will. Between myself and Jeb Bush or Ben Carson or anyone else, I will,” she added.

Hewitt said that he and moderator Jake Tapper of CNN have a “shared belief” that they will have failed if the story coming out of the Simi Valley debate is about them or their fellow questioner, CNN’s Dana Bash. Instead, he said, they want to bring the candidates into sharper focus.

“My number one goal is to represent a Republican primary voter who has not made up their mind,” Hewitt said. That voter’s top concern, he added, is “who would be commander in chief in a dangerous world.”

Hewitt has already found himself in a contretemps with Trump, after an interview Thursday in which the radio host asked the Republican front-runner a series of detailed questions about foreign policy. Trump bumbled a number of them, including one in which he apparently confused Iran’s elite Quds Force with the Kurds.

Hewitt, who has conducted more than 70 interviews with GOP hopefuls this year, put the same questions to Fiorina, who handled them with ease.

All of which got a typical re­action from Trump. He tweeted: “Why would a very low ratings radio talk show host like Hugh Hewitt be doing the next debate on @CNN. He is just a 3rd rate ‘gotcha’ guy!”

Philip Rucker contributed to this report.