A key group backing Florida Gov. Ron DeSantis’ presidential bid bet at the outset of his campaign that the path to the nomination ran through literally out-knocking the competition on his behalf.

So it did. In early-voting states, the super PAC Never Back Down blanketed the ground with canvassers who knocked on hundreds of thousands of doors again and again (and in some cases, again and again after that), hoping to spread DeSantis’ message and better introduce him to the electorate.

Never Back Down, which runs much of DeSantis’ ground game, planned to spend $100 million carrying it out, and it invited reporters inside its door-knocking boot camp in Iowa. The group says it has hit 812,000 homes in Iowa — more than half of the total number of households in the state. A similar share was hit in South Carolina, where the group says it knocked on more than 968,000 doors. In New Hampshire, another 385,000. And while there have been a series of leadership shake-ups at the super PAC, it has remained focused on its field operation.

Some allies say they remain buoyed by the ground effort, particularly in Iowa, where the group has gathered 30,000 commitment cards from voters pledging to caucus on DeSantis’ behalf and a growing bench of precinct captains willing to speak on his behalf at caucus locations.

Three people who were involved in the group’s early-state canvassing, however, see a futile effort — one where no amount of door-knocking can change what the polls show: former President Donald Trump trouncing the field.

“People underestimated the core support [for Trump],” said a Republican field operative who worked on the pro-DeSantis effort in an early state, noting that “everyone pinned their hopes” on the door-knocking effort being able to move the polls. “And it could not be overcome.”

NBC News spoke with more than a dozen people about the state of the GOP ground game in the weeks leading up to the Iowa caucuses, where Never Back Down’s strategy will face its toughest test yet. Only now, there’s stiffer competition going door to door.

All in on Iowa 

Until last month, Nikki Haley lacked a strong field operation. But she essentially received a whole army when the advocacy arm of Americans for Prosperity endorsed the former U.N. ambassador and pledged its grassroots muscle to help her on the ground.

The group says it has so far reached about 325,000 voters in the early-primary and Super Tuesday states, targeting people who previously supported Trump but are concerned he would lose in a rematch with President Joe Biden.

Drew Klein, an Iowa-based senior adviser for AFP, said the group will have 100 to 150 people at a time in the field canvassing for Haley in the state, an effort that’s been underway since its endorsement. The group has been out door-knocking and phone-banking since February — well before it endorsed Haley — seeking data on voters open to a Trump alternative.

Then there’s Trump, who has a couple of significant advantages over his rivals when it comes to ground efforts.

His team has tapered off door-knocking in Iowa but is continuing substantial door-knocking and phone-banking efforts in New Hampshire and South Carolina. The campaign says it has made hundreds of thousands of voter contacts in each early state.

Campaigns use door-knockers — volunteers or hired hands who go out to rally supporters to the polls and collect survey data — to gather intelligence and juice voter turnout. After the 2012 election, an academic study found that the presidential campaigns increased turnout by roughly 7% in areas they heavily canvassed.

In conversations with each of the campaigns or the outside groups backing their on-the-ground efforts, it was clear there was a new paramount focus in Iowa: recruiting precinct caucus captains to bring neighbors to caucus sites on Jan. 15 and speak on their candidates’ behalf there.

Trump’s strategy is centered on a “10 for Trump” plan, enlisting 1,800 precinct caucus captains across the state and providing each with a list of 10 first-time caucusgoers to turn out.

Haley’s campaign is also doing regular caucus trainings, said Emily Sukup Schmitt, co-chair of “Women for Nikki” in Iowa, explaining that it’s focused on both turning out voters and finding precinct captains.

DeSantis’ allies are focused here, too, with a person familiar saying the goal is to be two-deep with precinct captains at every location, ensuring that if one person is not properly engaging, they have a backup plan. With Iowa viewed as a make-or-break state for DeSantis, his allies have pulled resources from elsewhere to focus them there. Three people familiar with this development said Never Back Down recently relocated door-knockers from South Carolina to Iowa. One super PAC official said the goal is to have hit every targeted home at least five times before the Jan. 15 caucuses.

“It cannot be overstated,” the DeSantis ally said of the ground effort’s importance to their overall hopes.

Never Back Down strongly pushed back on claims that its efforts are falling short, misguided or futile, noting it has more than 100 full-time, paid canvassers working in the early states.

“Gov. DeSantis’ opponents will stop at nothing to undermine the fact that we’ve built the largest, most advanced grassroots and political operation in the history of presidential politics,” Never Back Down spokesperson Jess Szymanski said. “Our canvassers have knocked almost 3 million doors nationwide, which far surpasses any other political operation by miles, and are building support for DeSantis home by home across Iowa, New Hampshire and South Carolina.”

Trump’s ‘tremendous edge’

Trump continues to hold two big advantages over his opponents — the first being that he has a much larger base of volunteers.

“It gives us a tremendous edge,” Alex Latcham, Trump’s early-states director, said. “Our supporters are people who will wait in line to attend a rally to see President Trump for eight-plus hours. You know they’re going to go out and door-knock, right?”

The second amounts to what needs to happen in voter interactions. For Trump, it’s a strict get-out-the-vote model, getting existing Trump supporters to show up at the polls. For DeSantis and Haley, they not only have to do turnout efforts, but they also have to convince voters to shift away from the former president.

“It’s a much different experience for Trump supporters who are knocking on doors and doing all this great work making sure people show up to caucus on Jan. 15,” Jason Miller, a senior adviser to his campaign, said. “Whereas all of our opponents are put in this awkward spot of trying to get people to actually go and change their vote and go in a different direction, which is a much heavier lift.”

The dichotomy can be seen in AFP Action’s door-knocking script, which was provided to NBC News. When a voter tells an AFP door-knocker they support Trump, canvassers are tasked with presenting a response that reads, “We must beat Biden, but I’m concerned that with all of Trump’s baggage, Trump will energize Democrats and turn independents off. He’ll lose swing states in November, and we will be stuck with four more years of Biden, or even worse Kamala Harris. Don’t you think it’s time we nominate a new leader that can beat Joe Biden?”

Only if they say yes does the canvasser then begin sharing a message about how Haley is well-positioned to beat Biden.

Candace Carroll, the South Carolina state director for AFP Action, said her group is encouraged by what it’s hearing at targeted doors in interactions with Trump supporters or voters who have previously backed Trump.

“Most are either proactively telling us that they are supporting Gov. Haley or they are open to the idea of supporting her,” she said. “It’s very rare that we find someone who digs in their heels and isn’t willing to discuss or consider other candidates.”

‘I don’t think anyone will ever do this again’

DeSantis’ allies’ hopes are tied to just how much they’ve engaged with voters in places where ground games typically have not gone — often in rural areas that are tougher to canvass, with residences spread further apart. In Adair County, GOP chair Ryan Frederick, who has backed DeSantis, said the Florida governor was “the first guy to have a guy come to my door.”

“I live in a town of 400 people in the middle of absolute nowhere,” he said. “And he’s the first guy to run for president ever who’s actually had a dude show up at my door and ask if I’m interested in voting for him. And not only did they show up once; they showed up twice.”

Others, however, see that strategy as part of the candidate’s downfall. One person who formerly worked on an early-state door-knocking effort on DeSantis’ behalf said Never Back Down “wasted tens of millions of dollars, essentially chasing rural voters who had no interest in Ron DeSantis whatsoever.”

However, this person said the original door-to-door plan — introducing DeSantis to a wide range of voters at their homes — made a lot of sense if executed correctly. They just didn’t think it was.

“The problem was the super PAC and goal was not set up and executed properly,” this person said. “I don’t think anyone will ever do this again.”

Just how effective Republican canvassing efforts are continues to come under scrutiny. A wide-ranging NBC News investigation this year found that large-scale conservative canvassing efforts have been plagued with issues including fraudulent and untrustworthy data entries. But Republicans have insisted on its usefulness when done well, and high-dollar donors have been willing to open their wallets to fund the efforts.

Those issues blew up earlier this year when a paid Never Back Down door-knocker was filmed at a home in South Carolina saying to his friend on speakerphone that he was “a little stoned” and did not care about a property owner confronting him for breaking a “no solicitation” policy.

In any case, with Trump up double digits nationally and in the early states, even committed canvassers are questioning whether anything can dent his advantage.

“A few months is a lifetime in politics, but they’ve been waiting for months and months for things to change on the ground and with the sentiments of people,” one of the former Never Back Down-aligned canvassing operators said. “But it just hasn’t.”