The right-leaning laborers who helped elect Donald Trump to the presidency in 2016 are starting to sour on the real estate scion — truck drivers and farmers.

"He has not affected our business in a positive way," one truck driver, who asked for anonymity to protect their small business, told Business Insider. "He's killing our business. If consumers aren't buying, then there is no demand. This really isn't about my political leanings — it's pure business."

On Monday, Trump reportedly had to have a two-hour Cabinet meeting about increasing blowback from farmers. Trump campaigned in Iowa with the promise to support ethanol, which helped secured the vote from the state's 140,000 farmers, who are largely involved in corn.

Read more: Truckers voted for Trump in droves. Now they say his trade war is 'killing' their ability to make a living.

As Reuters reported, there's a "tide of rising anger in Farm Belt states" after the administration ruled this month to allow oil refineries to use a smaller amount of ethanol while mixing gasoline. Iowa Sen. Chuck Grassley didn't mince words on the topic: "They screwed us."

Even before the ethanol decision, farmers have been speaking out against the president. Bloomberg reported earlier this month that Agriculture Secretary Sonny Perdue was confronted by a group of enraged farmers at a fair in rural Minnesota.

U.S. President Donald Trump delivers remarks in support of farmers and ranchers in the Roosevelt Room at the White House May 23, 2019 in Washington, DC. Chip Somodevilla/Getty Images

Farm income in the US dropped to $63 billion in 2018, which is about half its 2013 level. That's a 16% dip from 2017, according to USDA data.

Soybean, grain, dairy, and livestock farmers in particular have been slammed in the Trump trade war, which will add 10% tariffs on some $300 billion of Chinese goods. In response, China's imports of US agricultural goods are down 20%.

Read more: The 'bloodbath' in America's trucking industry has officially spilled over to the rest of the economy

Government subsidies have been directed to relieve farmers whose wages have been hampered, but farmers say it's not enough. Bob Kuylen, a farmer of 35 years in North Dakota, told CNBC in Aug. that government subsidies for his 1,500-acre wheat and sunflower farm covers $15 per acre. Kuylen lost $70 per acre this year, however.

"It's really, really getting bad out here," Kuylen told CNBC. "Trump is ruining our markets. No one is buying our product no more, and we have no markets no more."

Truckers are moving away from Trump. J. Pat Carter/AP

Trucking has suffered in 2019, too. Some truck drivers attribute this downturn in the market to Trump's trade war.

Transport research groups reported that the volume of trucks purchased in July fell to its lowest level in nearly 10 years. The number of loads needing to be moved in the spot market tumbled by 37% this July compared to one year ago, and rates have fallen by as much as 18%.

The Cass Freight Index says year-over-year trucking volumes have slipped for eight consecutive months. In June, factory-activity growth was its slowest since October 2016, according to the Institute for Supply Management. That means manufacturers didn't receive as many orders and there were fewer things to move.

Read more: Amazon has quietly ordered 2,000-plus vans to deliver your Prime packages — and UPS and the Postal Service should feel stressed

Analysts say truckers are seeing their pay drop not because of the trade war, but because of other factors specific to the trucking industry. Experts have said an exceptionally vibrant 2018 may be the bigger reasons for the downturn in trucking. Last year, trucking was incredibly profitable, with record-low bankruptcies, remarkably high rates, eight-month-long wait lists for new trucks, and huge bumps in trucker pay.

Alienating a key demographic

Truck drivers and farmers are two of the most conservative jobs in the US. A Verdant Labs analysis of Federal Elections Commission data found that nearly three-quarters of farmers and truck drivers are Republican.

About 75% of truckers said they planned to cast their ballots for Trump, according to an Overdrive magazine survey from 2016. It's not clear how many farmers did the same, but more than 75% of voters in the Farm Belt states voted for Trump.

Both groups are politically influential. Farmers are so involved in trade discussions and lobbying that Smithsonian Magazine called agriculture "a political weapon." Four farmers ran for Congress last year. And the agribusiness industry as a whole has spent $2.5 billion in lobbying from 1998 to 2019 — $100 million more than defense.

Read more: FedEx is officially sounding the alarm bells on Amazon after years of laughing off the retail giant's rapidly building package-delivery empire

Trucking has its strengths in numbers. Some 1.8 million Americans are long-haul truckers, and they're highly engaged. Among the segment of truckers called owner-operators — who are independent, rather than company drivers — nearly 90% are registered voters and more than half have contacted an elected official on an issue.

Trump secured the presidency in 2016 in part because he campaigned among both groups. But alienating that demographic might cause further pain in his quest for re-election. Several polls indicate that Trump is "losing voters" to progressive Democratic candidates like Sens. Elizabeth Warren and Bernie Sanders.

"With these countries not buying American goods, and American companies not making major purchases, he created a bad deal for businesses that rely on our trade with these countries," Georgia-based truck driver Eric Wedlowe told Business Insider.