The Republican race is becoming a complete free-for-all, with all eyes trained on one key state

Presidential contenders who are members of the Republican Party's so-called establishment are growing increasingly snippy as their eyes train on what's looking more and more like a make-or-break state: New Hampshire.

Over the past week, New Jersey Gov. Chris Christie (R) sniped at Sen. Marco Rubio's (R-Florida) poor Senate-attendance record. Former Florida Gov. Jeb Bush's (R) allies went after not only Rubio, but also Christie and Ohio Gov. John Kasich (R).

And Rubio's campaign referred to Bush's operation as "sad."

"It's sad to see Jeb's 'joyful' campaign reduced to such intellectual dishonesty," Rubio spokesman Alex Conant said on Tuesday, responding to a what the Rubio campaign felt was a factually incorrect attack ad released by the pro-Bush super PAC, Right to Rise USA.

The uptick in sparring has come less than 50 days before voters cast their ballots in New Hampshire, perhaps the most important state for these four "establishment" contenders who've been upended by the shocking rise of the party's "outsiders" in the 2016 election cycle. Next week, every major presidential candidate is set to visit the Granite State.

Amid the rise of real-estate magnate Donald Trump - and, to a lesser extent, Sen. Ted Cruz (R-Texas) - the establishment-oriented candidates are intensely jockeying to put themselves in position to win New Hampshire's primary. Because of Trump's dominance, many candidates would probably be happy to grab a strong second-place finish there in order to rally the GOP establishment behind the runner-up.

New Hampshire could become especially significant if Trump or Cruz were to win Iowa, the first caucus state. Right now, Trump is neck and neck with Cruz in Iowa. But the businessman is up by about 14 points over his rivals in New Hampshire, according to a RealClearPolitics average of recent surveys.

Faced with the possibility of two Trump victories in a row - or a split between Cruz and Trump - some in the party believe New Hampshire's outcome could lead to a rapid panic within the party's establishment to coalesce behind its best chance of beating back the GOP's insurgent wing.

In simpler terms: If one of the four establishment candidates separates himself from the pack in New Hampshire, he could quickly find himself in a head-to-head battle with Trump or Cruz.

"It would raise the stakes in New Hampshire," said Matt Mackowiak, a veteran Republican strategist and the president of the Potomac Strategy Group. "The establishment would have to quickly unite behind whoever does best [next to Trump] in New Hampshire. And what you'd see is a very rapid coalescing."

For his part, Bush seems to be going all-in to position himself as the alternative to Trump. He launched an aggressive assault on the front-runner in recent weeks. And Bush's campaign noted the contrast between Bush's and his rivals' approaches to Trump, such as Rubio's pass on taking an easy shot at Trump during the last debate, and Christie's statement that Trump "looks like a serious candidate."

The Bush campaign intensified its focus on New Hampshire and other key early states over the past week, shifting many of its Miami-based staffers to the four first-voting states. The campaign also moved much of its planned spending on television ads to on-the-ground operations in Iowa, New Hampshire, South Carolina, and Nevada.

By January, the Bush campaign will have around 20 staffers in Iowa, South Carolina, and Nevada, as well as a whopping 40-plus staffers in New Hampshire. That would be larger than the current Christie, Rubio, and Kasich campaigns combined, the Bush campaign noted.

"The campaign is building the best national ground game and infrastructure in the field, one that will allow us to be successful in the long run doing what serious, national campaigns must do to be competitive in the primary and general elections," said Bush spokeswoman Allie Brandenburger.

She added: "Today, given the fluid race and the spending decisions by outside groups, we are making strategic adjustments with our resources to ensure we are in the most competitive position possible. We are excited about the massive Jeb army that will be spreading his message to voters on the ground in the February states and beyond."

Other establishment candidates' focus on New Hampshire has long been evident. Christie's 36 trips to the Granite State amount to a higher tally than any other Republican candidate in the race, according to NECN. His time in the state appears to be paying off: He has surged into a tie for third place in the RealClearPolitics average of recent surveys.

And right behind Christie is Kasich, who has made 28 trips to New Hampshire and stands at fifth place in the polls there.

Both governors the past week came under fire by the pro-Bush super PAC, which unveiled an ad in New Hampshire that unfavorably compared their gubernatorial records to Bush's. The Kasich campaign responded by aggressively mocking Bush.

"The latest ad from Jeb's team forgot to check the box for 'Which governor is living in the past because he has no new ideas for fixing anything?'" Kasich campaign press secretary Rob Nichols said. "You only attack those you fear and who's beating you, so this latest attack by Jeb on Gov. Kasich only reaffirms the governor's strength in New Hampshire.

"It's actually flattering," he added.

Other Kasich campaign staffers went off on Twitter:

And a super PAC supporting Kasich, New Day for America, went even further in its response. The PAC knocked Bush's and Christie's "baggage."

"As for Governor Christie, his mishandling of his state budget and the 'Bridgegate' scandal have earned him a 60% unfavorable rating from those who know him best - the people of New Jersey," said Connie Wehrkamp, a spokesperson for the super PAC.

Rubio, meanwhile, has come under renewed fire for his Senate-attendance record as he has maintained a steady second-place standing in New Hampshire and the No. 3 position nationally.

The Florida senator found himself under attack from two establishment-friendly directions earlier this week.

Bush's super PAC unveiled a scathing ad that hit Rubio for missing national-security hearings in the wake of recent terror attacks in order to attend fundraisers. Christie also got in on the action on Tuesday, blasting Rubio for missing a vote on a spending bill.

"Dude, show up to work," Christie said at a town-hall event in Iowa. "If you don't want to, then quit."