Turlock, California (CNN) It was all going well for Democrat Josh Harder before he walked up to Stephanie Bull's door.

Harder was canvassing here in the southern reaches of the district he hopes to represent in Congress when the Turlock native was once again asked to take on a nagging question: Are you really from here?

It's an issue that has badgered the 31-year-old venture capitalist ever since he decided to try to oust Rep. Jeff Denham, a Republican who was swept into Congress on the Tea Party wave of 2010. And it highlights an important inflection point in the fight to represent California's 10th Congressional District, where both Democrats and Republicans in the heavily agricultural area are proud of having a separate identity from their more economically prosperous neighbors in nearby San Francisco, San Jose and Oakland.

That desire has forced all three top candidates (there are seven total) to defend their ties to the district.

The questions matter because this race is key to Democrats' hopes of taking back the House later this year. While Denham won reelection in 2016, President Donald Trump lost this district to Hillary Clinton by three percentage points, making Modesto, Turlock and a slew of other towns one of 23 areas in the country where Clinton won yet Republicans maintained control of the congressional seat.

That has national Democrats eager to score a win in the valley, where voters on June 5 will pick two candidates to move onto November's general election.

Denham is staking his candidacy on a push to force his own party leadership in Congress to take a vote on immigration reform, a national issue that is especially resonant in the district because instability in farm labor can have a direct impact on the farms that power the area. But voters in the district, some of whom with no ties to the farm industry, are also eager for candidates to prove their ties to the region.

"You are not from Turlock, right," Bull, a 39-year-old mother of two, directly asked Harder, who proceeded to give his now familiar spiel of growing up the son of an optometrist before leaving for college at Stanford University and later Harvard University.

He usually frames his time at Bessemer Venture Partners, a venture capital firm that is touted as the oldest in the United States, as time spent growing other businesses and now refers to himself as a part-time teacher because of his job teaching a class at Modesto Junior College.

"No," he said incredulously, like a man who has had to defend his roots countless times. "I was born here!"

Though Harder denies it, the questions clearly bother the first-time candidate. He often references his Turlock family in conversation and the first line of his campaign website talks about his great grandfather joining a wagon train to Manteca a century ago.

But Bull wasn't buying it.

"I want to vote for someone who is going to represent people in our area," said the Democrat sitting on her porch as her husband, John, took a chainsaw to a nearby tree. "Not people from the Bay Area."

While Harder is questioned about his time spent in the Bay Area, Denham, an imposing 50-year-old multi-millionaire who made his money running Denham Plastics in Salinas, is cast by his Democratic opponents as a coastal elite who only came to Stanislaus County to run for office years ago. Likewise, Michael Eggman, the other top Democrat in the race, has been nagged by questions about his home in Fresno County. Eggman, who is a third-generation beekeeper from the district, has explained the issue by saying his main residency is in Turlock, but he and his wife bought the house so his wife, a flight attendant, could more easily commute to Los Angeles for her job.

Virginia Madueño, the former mayor of Riverbank who is another Democrat running in the primary, was born in Modesto and has sought to raise questions -- albeit subtly -- about Eggman and Harder's ties to the district.

"I am not somebody who is new to the district," she told CNN. "I am not somebody who left and came back to try to establish a name and a relationship. I have been here."

Political operatives in the area explain it as voters wanting to have a separate identity from their neighbors.

"The Valley has a bit of a chip on its shoulder that we play second fiddle to the Bay and LA in state politics," said a top local Democrat supporting Eggman. "So they want someone they know is going to be a strong advocate for regional interests."

The beekeeper vs. the venture capitalist

Where Harder is polished and clean cut, Eggman is rough and rugged.

Though both speak highly of each other, they have little personally in common, a fact that contributed to Eggman's decision months ago to complicate Harder's run and try for a chance to challenge Denham for a third time.

"His profile just doesn't fit this district and that is why I am running again," Eggman said of Harder while standing over roughly 500,000 bees in a dozen box hives surrounded by a Turlock almond orchard.

The image is intentional and crafted. It would be impossible to avoid the fact that Eggman is a beekeeper. His lawn signs are adorned with a bee buzzing in the California sun and in a slight against Denham -- whose signs read "Local Farmer" in block letters -- some of Eggman's now feature "Real Local Farmer" next to the bee.

A protester holds a sign outside of a casual "Coffee and Conversation" with U.S. Rep. Jeff Denham (R-CA) at the Riverbank Teen Center on May 9, 2017 in Riverbank, California.

Eggman drives around in an aging pick-up truck named Jethro with no air-conditioning, a permanently down passenger window and GMC is faintly spray-painted on the back. And he will happily attack Denham's ties to the district.

When an aide casually mentioned that Denham's company is based in Salinas, Eggman chimed in.

"By the coast," he said, a not-so-subtle hint that things are vastly different 100 miles away.

Eggman said it was conversations in these orchards with the predominantly Latino farmhands that convinced him to run another time.

"When I work, I get results. When they work, they get results," Eggman said. "So they take issue with someone that talks a lot but doesn't deliver any results. They are saying it is time for a new jefe."

But to some Democrats in the district, the bee farmer has the stain of a losing candidate on him after losing to Denham in 2014 and 2016.

"I think it is pretty clear that we can't lose this district a third time in a row," Harder said in between door knocking stops. "And I think what we have seen is a real rallying around our campaign to actually make sure we actually beat Denham."

Trump's election and subsequent time in office, often defined by rhetoric on immigration that has alienated some Republicans and activated other non-traditional voters, has both Democrats believing now is the time they can take down Denham.

"Trump changed everything," Eggman said. "And the fact that Denham has voted with Trump over 97% of the time."

Harder agreed but said, in a subtle knock against Eggman,v that no previous campaign has held Denham accountable.

"Denham talks like a moderate (but) he votes like a radical," Harder said.

'A farmer from the district'

After stepping out of church at House Modesto on Sunday, Denham was as confident as his aides say he always is. It's a confidence that comes with winning reelection routinely but belies his position as a vulnerable Republican running for re-election.

Denham is making immigration a cornerstone of his campaign to represent the over 40% Latino district. By using an arcane Congressional rule known as a "discharge petition," Denham is looking to force a vote on a plan that finds a permanent solution to recipients of the Deferred Action for Childhood Arrivals program, a Barack Obama-era program that Trump ended. The fate of the program, which offered protected status to children brought to the United States illegally, is tied up in the courts, but Denham wants to force Republicans to take on the hot button issue and, then, tout himself as an immigration reform champion.

By taking on immigration, Denham is tackling an issue that animated Trump's presidential campaign and putting himself at odds with the President whose tenure has put pressure on him.

"You have to fight for what you believe in and I think this is something that has to get done," he said of his push in Modesto. "I'm willing to stand up to my own party."

Democrats like Harder and Eggman laugh at comments like this.

"It is nothing more than an election year tactic, which we have seen before from him," Eggman said.

But Denham says he is unmoved by their calls of political opportunism.

"Look, if this issue costs me my reelection but we get it done, I'll be happy with that," he said. "I just want to get it done."

Rep. Jeff Denham talks with constituents during a casual "Coffee and Conversation"

Though the congressman won reelection in 2016, he said he was taken aback by the "drastic change" in Democratic interest in the district in recent years.

"People who have never voted for came out and voted and it really showed me that we have a lot of people to talk to," he recalled. Democrats have accused Denham of dodging his constituents, pointing to one event he did last year that resulted in pointed questions and protest.

Denham, who is a shoe in to move on after the June primary, is staking his campaign on a mix of loyalty, both to Trump and from his constituents, his recent immigration push, and his branding as a "local farmer" who grows almonds.

Despite his own ties outside the district, Denham argued on Sunday that he has won because Democrats "continue recruiting people up from outside our area" to run.

"This is my community," he said. "We go to church here, we shop here, my kids have gone to school here."

When asked whether he was worried more this year than in previous years, he pointedly took a shot at his competition.

"When they find a farmer from the district," he said with a smile, "then things will get difficult."