Democrat Andrew Janz is confident he’s well on the way to defeating eight-term Central Valley Republican Rep. Devin Nunes, a favorite of President Trump.

Now he has to convince Democratic Party leaders.

Janz, a Fresno County deputy district attorney, has had plenty of success raising money from Democrats across the country. But he says he’s been almost invisible to the Democratic Congressional Campaign Committee, which makes the decisions when it comes to doling out party money to House candidates.

Janz, who was in San Francisco’s Dogpatch neighborhood recently for a fundraiser, said he is more concerned than angry.

“I’m worried about their lack of interest in a most compelling contest” against an opponent who “is universally hated in Democratic circles,” Janz said.

The 44-year-old Nunes, R-Tulare, has drawn the scorn of Democrats as chairman of the House Intelligence Committee, a perch from which he’s led the effort to quash Special Counsel Robert Mueller’s investigation into Russian interference in the 2016 presidential campaign.

Party leaders decide which campaigns are likely to succeed and make funding decisions accordingly. Janz fears that Democratic officials have put his race in the too-big-a-reach category.

Democrats are looking at a huge midterm battlefield of more than 100 competitive seats, and all their funding decisions are aimed at flipping the 23 GOP-held seats needed to retake control of the House.

Party officials say the right things about Janz and his campaign.

“The DCCC trusts candidates to run campaigns that work best for their individual districts, which is exactly what Andrew Janz is doing,” said Amanda Sherman, a spokeswoman for the committee. “Andrew Janz has built a strong, independent, Central Valley-focused campaign that will make this race competitive.”

The party’s actions, however, haven’t matched those words. When former President Barack Obama visited Orange County this month for a congressional campaign event, Janz wasn’t one of the seven party hopefuls invited. He’s also not one of the eight Californians on the party’s Red to Blue list of “top-tier candidates” slated to receive organizational and fundraising support.

There are plenty of reasons for Democratic officials to conclude that the 34-year-old Janz, making his first run for public office, is an unlikely candidate to unseat Nunes, who has been invincible at the ballot box since he was first elected in 2002.

The 22nd Congressional District, which includes much of Fresno and Tulare counties, tilts strongly right, with registered Republicans outnumbering Democrats, 42 to 32 percent. In 2016, Trump beat Hillary Clinton there, 52 to 43 percent, and Nunes was re-elected with 68 percent of the vote.

The June primary didn’t indicate much had changed. Nunes topped Janz easily, 58 to 32 percent.

Of the major political rating services, only one, Sabato’s Crystal Ball, lists the Central Valley race as competitive. And even it figures the contest as “likely Republican.” The $6.1 million that Nunes had in the bank on June 30 also boosts his chances.

But Janz hasn’t backed down, arguing that he will pay more attention to the district’s concerns than Nunes, who has devoted much of his time to his high-profile job in Washington. Janz had $1.1 million in his campaign account at the end of June and has been one of the Democrats’ strongest online fundraisers, pulling in more than $1 million in August alone.

In the heavily agricultural district, water is the main concern, whether it’s clean water for drinking, dams for storage or canals to get farmers the irrigation they need. Trump’s tariffs raised the possibility that growers of such local crops as almonds, grapes, raisins and pistachios could lose overseas sales. And immigration reform is on everyone’s list, Janz said, because Central Valley farmers “want a reliable source of labor and are tired of (Immigration and Customs Enforcement) raids.”

“I’ve been talking to everyone,” he said. Democrats have a special dislike for Nunes for his close ties to Trump, Janz said, and “Republicans are frustrated about Devin Nunes’ inability to get anything done for the district.”

That’s not the way Nunes and his supporters see it. He touts his connections to Trump as a plus for his district. While campaigning for other Republicans, he has warned that a GOP-led House could be the only way to ensure the president’s programs are passed.

In a video spot, Nunes said it’s Janz who ignores his district’s interests by allying with Hollywood and San Francisco Democrats, “the very people who want to cut off the valley’s water supply.” The district supports Trump, Nunes says, but Janz’s main backing comes from “far-left resistance activists.”

An ad on Nunes’ Facebook page talks about how his office helped a family in the Fresno suburb of Clovis with a Veterans Affairs problem. His history as a part of a longtime local farming family also plays well.

Democratic officials have no reason to dismiss his chances, Janz says. He points to a survey taken for his campaign this month by Strategies 360 that found Nunes with just a six-point lead, 50 to 44 percent.

“I started out 36 points down, and now the polling shows a continuing trend toward victory,” Janz said.

Janz has also been much more visible in the district than Nunes, who has spent much of the year in Washington.

“We’ve had 130 stops in coffee shops and backyards and 10 town halls,” said Heather Greven, Janz’s campaign manager. “We’re putting boots on the ground, with 250 people in someone’s backyard six nights a week.”

Enthusiasm doesn’t always translate into votes, however, especially in an area where the GOP — and Nunes — have held control for so many years.

“We’re under no illusions,” Greven said. “This is a tough district.”

John Wildermuth is a San Francisco Chronicle staff writer. Email: jwildermuth@sfchronicle.com Twitter: @jfwildermuth