Donald Trump has passionately disputed a shock Iowa poll that found Kamala Harris leading the former president in the typically red state 47% to 44%.

“No President has done more for FARMERS, and the Great State of Iowa, than Donald J. Trump,” Trump said in a post on his Truth Social network on Sunday morning. “In fact, it’s not even close! All polls, except for one heavily skewed toward the Democrats by a Trump hater who called it totally wrong the last time, have me up, BY A LOT.”

Trump continued, in all caps: “I love the farmers, and they love me. And they trust me.” More than 85% of Iowa’s land is used for farming and it produces more corn, pigs, eggs, ethanol and biodiesel than any other state.

On Saturday, the Selzer poll carried out for the Des Moines Register newspaper showed the vice-president ahead of her Republican rival by three points. Selzer is a widely respected polling organisation with a good record in Iowa; she shot to polling fame in 2008 when she predicted that a virtually unknown senator, Barack Obama, would beat frontrunner Hillary Clinton in the Iowa caucuses.

If Harris were even competitive in Iowa – which Trump won in both 2016 and 2020 – it could radically reshape the race.

The pollster told MSNBC on Sunday that Harris was leading in early voting in Iowa “because of her strength with women generally, even stronger with women aged 65 and older. Her margin is more than 2-to-1 – and this is an age group that shows up to vote or votes early in disproportionately large numbers.”

Earlier on Sunday, Trump’s campaign released a memo from its chief pollster and its chief data consultant calling the Des Moines Register poll “a clear outlier” and saying that an Emerson College poll – also released Saturday – more closely reflected the state of the Iowa electorate.

The Emerson poll found 53% of likely voters support Trump and 43% support Harris, with 3% undecided and 1% planning to vote for a third-party candidate.

The Trump campaign, which many Democrats believe is setting the stage for a series of legal challenges to poll results, also said in an email that the Des Moines Register poll and a subsequent New York Times swing state poll that found Harris ahead in four of the seven states, is “being used to drive a voter suppression narrative against President Trump’s supporters.

“Some in the media are choosing to amplify a mad dash to dampen and diminish voter enthusiasm,” the statement added.

Last week, Trump said: “Pennsylvania is cheating, and getting caught, at large scale levels rarely seen before” but did not provide evidence for the claim. A Harris campaign official said that the “cheating” claim was an example of how Trump was trying to sow doubt in the electoral system because he was afraid he would lose.

The claims come as a federal judge plans to rule on whether Iowa officials can continuing trying to remove hundreds of potential noncitizens from its voting rolls despite critics saying the effort could keep recently naturalized citizens from voting.

North Dakota governor Doug Burgum, a Republican, told NBC’s “Meet the Press” on Sunday that he is confident that Trump is “going to confidently win Iowa”.

Asked if Trump has a problem winning over women voters, Burgum said: “I’d be surprised, completely shocked if that comes anywhere close to being the fact in Iowa.”

Burgum pointed to national polling which shows Harris and Trump tied.

“I think that’s the feeling that I get on the ground. It’s a very tight race. It’s going to be decided on Tuesday,” Burgum added.

But speaking to MSNBC, Maryland governor Wes Moore, a Democrat, said the Des Moines Register poll putting Harris ahead Iowa, but still within margins of error, “lines up with what we’re seeing on the ground”, particularly among women voters.

Moore continued: “We’re watching an energy that I think has not been there for a while, where we continue to see where women understand firsthand, what is at stake, that they understand the dynamics and the distinctions between these two candidates literally could not be more stark about when you’re talking about a future vision for the country.”