Ms. Schmidt is fine with climate skepticism. “A key tenet for change,” she said, “is to meet people where they’re at.”

Mr. King was first ousted from his committee assignments, then defeated in a primary challenge, after a series of racist comments culminated in an interview with The New York Times in which he asked, “White nationalist, white supremacist, Western civilization — how did that language become offensive?”

But Ms. Schmidt said that Mr. King, after 18 years in Congress, remained influential in conservative western Iowa.

“I certainly never thought we’d be in a position to have a meeting where you have incredibly liberal socialists teaming with very right-wing QAnon believers,” she continued. “People have to open their minds a little bit, and sometimes they have to shut their mouths.”

How Republican presidential candidates respond is, at this point, anyone’s guess. Despite Mr. Trump’s more recent comments, when he was president, his administration said it had no plan to stop the pipelines. In fact, a tax credit created in 2008 to incentivize carbon capture programs like Summit, Navigator and Wolf was expanded by a budget law in 2018 that Mr. Trump signed, and expanded again by a tax bill signed by Mr. Trump in 2020. The credit was expanded yet again by President Biden’s Inflation Reduction Act.

Mr. Rastetter has donated around $10,000 to Mr. Trump’s campaigns since 2016, along with the hundreds of thousands he has donated to national and state Republican interests over the past 15 years.

Officials at Navigator declined to comment.

Critics say Mr. Trump has every reason to oppose the pipeline now. He has called climate change a “hoax” devised by China, so the pipelines are billed as a solution to a problem he does not recognize. Even better, he could use his stated opposition to continue a feud with Ms. Reynolds, whom he has blasted for refusing to endorse him, said Jane Kleeb, a Nebraska Democrat and anti-pipeline activist who has been pressing Mr. Trump to get involved.

“There’s no downside for him,” she said.

When Mr. Ramaswamy, who has called climate activism a cult, was asked about the issue last month in Davenport, Iowa, he dismissed the pipelines as a solution in search of a problem.

But in an interview this week, Mr. Ramaswamy did not blame economic and political interests in Iowa. They are merely responding to incentives set by the federal government, large states like California, and even climate-conscious European nations, he said.

“The debate in Iowa is just collateral damage,” he said.

Other candidates might have a tougher time threading that needle. The companies backing the pipelines frame them as a salvation for ethanol, which Iowa corn farmers depend on, in a world increasingly hostile to internal combustion engines.

One candidate, Gov. Doug Burgum of North Dakota, does not have the luxury of silence. He has already championed the Summit pipeline, which would end in his state, telling The Bismarck Tribune in May that two carbon dioxide pipelines have operated safely in the state for years.

“And then now it’s like these are the most dangerous things in the world,” he scoffed.