Even before facing Republican discipline in the House in January 2019 after the Times interview, Mr. King was in electoral trouble. He just barely won re-election in 2018 over Mr. Scholten, a former professional baseball player, by three percentage points — in a district Mr. Trump carried by nearly 30 points.
Just before the election, the head of the Republican House campaign arm, Representative Steve Stivers of Ohio, issued a highly unusual rebuke of Mr. King for his endorsement of the Toronto mayoral candidate, Faith Goldy, who has espoused white nationalism, and for comments seeming to embrace the “Great Replacement,” a far-right conspiracy theory. “We must stand up against white supremacy and hate in all forms, and I strongly condemn this behavior,” Mr. Stivers said at the time.
A paradox of Mr. King’s career is that, in his anti-immigrant language and policies, he was years ahead of Mr. Trump, who won the presidency by stirring fears about nonwhite immigrants.
Well before Mr. Trump promised to build a wall on the southwest border, Mr. King, who founded an earth-moving company, stood on the House floor and showed off a model of a 12-foot border wall of his own design.
Soon after Mr. Trump took office, he invited Mr. King — who even then was snubbed by establishment Republicans like the former House speaker John A. Boehner — to the Oval Office. The president boasted to Mr. King of having supported him, and raised money for him during an Iowa visit in 2014, Mr. King told The Times.
In the past, Mr. King routinely won the backing of other Iowa Republicans, including Gov. Kim Reynolds, who named him a co-chair of her 2018 election campaign. He sought to be a kingmaker in presidential politics given Iowa’s early-voting role, and in 2015 he endorsed Senator Ted Cruz of Texas, who went on to win the state’s caucuses over Mr. Trump.
“For two decades Steve King has been something of the sun in the political universe around here,” Douglas Burns, an owner of newspapers in Mr. King’s district, said on Tuesday night. “I’ll still have to see the eclipse tomorrow to believe these results.”