(CNN) Progressive insurgents were turned back by the Democratic establishment on Thursday in Delaware, where Sen. Tom Carper fended off a spirited -- but perhaps fatally underfunded -- primary challenge from the left by first-time candidate Kerri Evelyn Harris, CNN projects.

The governor for eight years before entering the Senate in 2001, and the state's lone US House representative for a decade before that, Carper began his run in statewide office, as treasurer, in 1977. After former Vice President Joe Biden, who endorsed him two weeks ago, Carper is probably Delaware's best-known political figure. A loss to Harris would have been the first of his long career.

Carper's Senate seniority and decades of experience were as much a burden as a selling point in the race, which kicked off in earnest earlier this year when Harris, a 38-year-old Air Force veteran and community organizer, entered pitching new blood and a different kind of politics. By almost any metric, ousting Carper would have been the Democratic left's most astonishing victory of the season, which helped Harris' cash-strapped campaign attract a late outside boost from the progressive Working Families Party.

Respectful, per Delaware's exacting demands for politeness in the political arena, but firm in her criticism, Harris, who is biracial and gay, had sought to cast Carper, 71, as an out-of-touch centrist who, for all his good intentions, is disconnected from "the urgency of now."

"We can't wait a little bit longer for a pay raise," Harris said in an interview on a searing hot Labor Day in Wilmington. "We can't wait a little bit longer for health care that we can actually afford to use. We can't wait a little bit longer for our children to be properly educated or for our climate to be clean. These things are necessary and they have to happen now."

The Ocasio-Cortez connection

Back in late June, Harris took a brief detour from her own efforts to stump alongside a little-known candidate in New York's 14th Congressional District named Alexandria Ocasio-Cortez . Both were running on platforms headlined by "Medicare-for-all" single payer health care, a $15 minimum wage, ending cash bail and a refusal to accept corporate political action committee donations.

When Ocasio-Cortez won her primary, a handful of organizers from her team traveled south to join Harris' small, feisty operation. Last Friday, Ocasio-Cortez hosted a pair of town halls with Harris in Delaware.

"She had my back and I'm here to have hers," Ocasio-Cortez said in Newark, "because that's how the progressive movement really works."

But the similarities between their contests were checked by Carper's relentless political retail work. Unlike New York's Rep. Joe Crowley, whom Ocasio-Cortez defeated, the three-term incumbent has over the years gone to great lengths, literally, to sustain his relationship with voters back home. He commutes almost daily from Wilmington to Washington, DC, and frequently touts the 482,000 miles he's put on his Chrysler minivan "traveling up and down the state."

Carper and his supporters had been quick to underline the differences between him and Crowley, a Queens Democrat with a home in Virginia who Ocasio-Cortez cuttingly alluded to in her viral campaign ad as someone who "doesn't send his kids to our schools, doesn't drink our water or breathe our air." They had also gently, but consistently over the last couple of days, sought to portray the Harris campaign as a front for out-of-state progressives.

"My gut tells me that they believe that Kerri is the next Alexandria Ocasio-Cortez and they believe that I'm somehow the next Joe Crowley," Carper said in an interview at a Labor Day picnic in Wilmington. "They think that Delaware is New York City. And I think they're mistaken on all three counts."

Sweat seeping through a green Navy flight suit, worn to honor the late Sen. John McCain, Carper -- now the Senate's only Vietnam veteran -- argued that voters in Delaware wanted two things he was uniquely positioned to provide: someone with the clout to shape compromise on Capitol Hill while also leveraging that power to "stop Trump from ruining this country."

"Delaware's almost schizophrenic, and I think the country is too. They want us to stop Trump from doing more stupid and, in some cases, cruel things, at the same time they want us to try to find common ground on a number of other issues," he said, ultimately landing on an optimistic note: "And I think you can do both. I think you can do both."

To say Harris offered a different view of the current landscape misunderstands, or at the least underestimates, the fundamental clash at the heart of this contest -- and so many others in what has been a remarkable season of upheaval in Democratic politics. Harris was critical of Carper's record, including two votes in particular that favored the banking industry and pharmaceutical companies, but the roots of her challenge ran deeper.

A different kind of politics

Their exchanges at a debate last week, the only one of the campaign, made clear the ideological and stylistic gulf. When Harris, in response to a question about college costs, said she would push for the elimination of all student debt, Carper dismissed the suggestion as plainly unrealistic.

"I don't have a magic wand that would enable us to do that," he said. "It would cost a pretty penny."

"What bothered me," Harris said days later of his response, "is that there's this idea that these are extreme ideas. But they only seem to be extreme for those who are multimillionaires living in Congress. They don't feel extreme to the people that you speak to in the streets. ... We see that 'magic wands' are always available and present when corporations win."

She also criticized Carper's vote in 2006 to elevate current Supreme Court nominee Brett Kavanaugh to the US Court of Appeals for the District of Columbia Circuit. Carper was the only Democrat still in the Senate to cross party lines.

Asked during the debate why he had backed Kavanaugh then, Carper said his decision turned on the guidance of distinguished Delaware Judge Walter Stapleton, for whom Kavanaugh had clerked, and other respected jurists from the state.

"I voted my hopes over my fears," he concluded. "I will not do that again."

At the debate, Harris returned to Carper's explanation when questioned about her inexperience in elected office, suggesting that his vote on Kavanaugh and, more recently, to back former drug company executive Alex Azar as the new secretary of health and human services underlined the need for a "diversity of experience."

"It's scary when you hear him say, 'I voted for Kavanaugh because all of his people (vouched for him),' " she said on Monday. "That's also the excuse for why he voted for Azar. He said he knew someone who went to Yale with him and said he was a good guy. If that's your reason for voting on things that can affect all of our lives, that's a problem."

Carper said in a statement after the confirmation vote that he believed Azar was qualified for the job and shared his desire to transform the health care system "to one that rewards health care providers based on the quality of care patients receive."

The shadows of 2010?

Delaware is no stranger to unexpected primary challenges -- or bewitching outcomes.

The state has mostly elected some combination of the same handful of leading politicians, from both parties, over the past few decades. But as the Harris challenge gained steam, chatter increased about the fate of Republican Mike Castle, the former governor, lieutenant governor and congressman whose defeat in 2010 to a tea party outsider effectively squandered what had been viewed as a winnable Senate seat.

Eight years on, Democratic Sen. Chris Coons, who defeated Republican nominee Christine O'Donnell that November, warned that a win for Harris on Thursday could similarly imperil what's now considered a safe Democratic seat.

"I think it would be dramatically harder for (Harris) to win in November than Tom Carper," Coons said in a phone interview. "I think there were a number of Delaware Republicans who voted for Christine O'Donnell in 2010 to send a message to Mike Castle, that they wanted him to be a little sharper, little more conservative, little more ideologically pure. But they didn't imagine that they were handing the seat away."

The Harris campaign rejected any claim that her nomination would open the door for the eventual Republican nominee, which CNN projects Thursday night will be Sussex County Councilman Rob Arlett, who was President Donald Trump's state chairman in 2016.

Joe Dinkin, campaigns director for the Working Families Party, which through its independent expenditure committee backed Harris with $100,000 in field work, direct mail, texting and digital advertising in the home stretch of the campaign, dismissed Coons' warning as "preposterous" and the campaign pointed to polling that suggested Harris would have started the general election campaign with a lead.

Even with the late rush of support, Harris' campaign entered primary day having been outspent by something like 20-to-1, according to Federal Election Commission filings. Carper also boasted nearly every big ticket endorsement the state has to offer, from Biden to the Delaware AFL-CIO, the Planned Parenthood Action Fund and the state teachers union. The Working Families Party's outlay alone nearly matched Harris' total fundraising, which came in at around $120,000.

"We're investing substantially in the race because Carper is operating a version of the Democratic Party that might've passed muster in the 1990s," Dinkin said. "But it is not the direction progressives want to see right now."