Iowa was not on anyone’s bingo card of 2020 battlegrounds.
Donald J. Trump carried the state by nine percentage points in 2016, and a year ago prominent Democrats in the state passed up the chance to challenge Senator Joni Ernst, a popular Republican seeking re-election.
But with the political ground shifting precariously under Mr. Trump amid multiple crises, Iowa is unexpectedly in play in the presidential and Senate races this year, moving Republicans to high alert. Democrats, who a few years ago were shrouded in despair that their party might never again appeal to white working-class voters, are energized.
A poll published by The Des Moines Register and Mediacom on Monday showed Mr. Trump with only a one-point lead in the state over former Vice President Joseph R. Biden Jr. The poll revealed a deep erosion of support for the president among white women without college degrees, voters who were key to his 2016 coalition across a swath of Midwestern swing states.
The same survey showed that Ms. Ernst, a rising star in her party in her first term, was narrowly trailing her little-known Democratic challenger.
Theresa Greenfield, the Democratic Senate nominee who emerged from a primaryon June 2, is running primarily on a biography with parallels to the one Ms. Ernst used to introduce herself to Iowans six years ago: Both grew up on farms, and both have made promises to show Washington their scrappy values of hard work and self-reliance.
But Ms. Greenfield is turning Ms. Ernst’s celebrated anti-establishment catchphrase against her rival.
“Senator Ernst told Iowans in 2014 she was going to be independent and different and she was going to ‘make ’em squeal,’” Ms. Greenfield said in an interview, echoing a television ad six years ago in which Ms. Ernst said she would take a knife to federal spending the way she castrated hogs on the farm. “The bottom line is nobody’s squealing except Iowans.”
Ms. Ernst declined an interview request. But her advisers noted that Ms. Greenfield, a businesswoman and political newcomer, was riding the crest of more than $7 million in positive TV ads by liberal outside groups.
“This is Greenfield’s high-water mark,” said David Kochel, a senior adviser to the Ernst campaign. He promised that the Democrat would soon face a barrage of negativity. “Forty percent of Iowans don’t have an opinion of Theresa Greenfield,” he said. “We’re here to help.”
In the Des Moines Register poll, Mr. Trump led Mr. Biden 44 percent to 43 percent among likely voters, the latest in a wave of national and state polls showing the president’s prospects for re-election at their most precarious all year.
Although the road to the White House in November will not hinge on Iowa, with its meager six electoral votes, the tightness of the race in the state is an ominous sign for Mr. Trump in other Midwestern battlegrounds like Ohio and Wisconsin, which also have large electorates of older and rural voters, and white voters without college degrees.