Election Day diesel and gasoline prices helped push Americans toward Democrats in Tuesday's midterms, with voters citing the cost of living in their decisions, exit polls showed.

Only last month, President Donald Trump bragged at a campaign rally that the US oil and gas business was making hundreds of billions of dollars in the wake of the Iran war, saying, "We're making a fricking fortune," and that fuel prices would come down.

But many voters in rural states who depend on diesel, gasoline and heating oil to earn a living and warm their homes could not wait for his promised fuel-price drop.

Democrats captured majorities in both the Senate and House on Tuesday, scoring sweeping victories that reached deep into Republican strongholds as tens of millions of voters delivered a scathing rebuke to Republican Trump.

Nearly 9 in 10 voters identified the cost of living as a crucial or major factor in their vote, according to exit polls conducted by SSRS on behalf of a consortium of US media outlets. Many said they felt worse off than two years ago.

Prices for both diesel and gasoline were at their highest level ever on an Election Day, according to price tracker GasBuddy, surpassing levels in 2022 and pushed higher by the Iran war and Russia's war in Ukraine.

When diesel is high it can boost inflation as it is burned in farm equipment, fishing boats, and trucks and trains that haul goods across the country. Heating oil warms homes in key northern states such as Maine, where voters in the US Senate race opted for Democrat Troy Jackson, who beat Susan Collins, a Republican who served nearly 30 years.

Soaring diesel costs helped convince farmers to back Democrats, said Donn Teske, president of the Kansas Farmers Union for the past 25 years. High costs for fuel and other inputs, such as fertilizer, make it hard for farmers to make a living, said Teske, who voted for Adam Hamilton, the first Democrat elected to the Senate from Kansas since 1932.

"That price of diesel, it goes way beyond what goes in the combines and the tractors," said Teske, 71, whose family raises cattle near Wheaton, Kansas. "It's the trucks that run up and down the road, and what the consumer has to pay for gas at the pumps that eats in to their family budget."

"All the farmers have families too, and you're trying to keep the kids fed ... and it's just gotten frustrating for everybody." Last month, Trump announced an $8 billion financial support program for farmers to offset high diesel costs during the autumn harvest season. But a Trump administration official said late last month that the aid would not be disbursed until after the election. And farmers said on Wednesday they did not know whether the aid would cover all of their increased costs. "It's a Band-Aid," Teske said.

While Trump seemed powerless to significantly lower fuel prices ahead of the election, Democrats did not offer solutions of their own to quickly dampen prices.

Democrats such as Jackson in Maine pointed to Republicans' support for the war in Iran. Collins said she voted several times to bring the war to an end after initially supporting it.

Dan Atkisson, who grows grain sorghum near Stockton, Kansas, said he voted for Republican incumbent Roger Marshall for US Senate but that it was impossible to avoid high diesel costs.

"At the end of day, you still have to use diesel fuel to plant, to harvest, to spray, to haul the grain away," said Atkisson, 41. "You just don't have another option." Jamie Ager, a Democrat who flipped North Carolina's 11th congressional district on Tuesday, told Reuters in an interview that he heard from farmers and other rural residents that high fuel prices were among the key reasons that they were interested in his campaign.

"Obviously, the cost of fuel and diesel fuel was a lot, the fertilizer crisis this spring when people were putting a lot of crops in the ground," he said, referring to a spike in prices for fertilizer, which uses natural gas as a feedstock, driven up by the wars. "The economic landscape for so many farmers was rough."