Eighteen U.S. House races — including three in Iowa's agriculture-heavy economy — shifted toward Democrats in Cook Political Report's Friday ratings, with the nonpartisan forecaster projecting a Democratic pickup of 9 to 19 seats next month.

That range would yield 224 to 234 House seats for Democrats. Republicans hold 218, with Democrats at 214, one independent, and two vacancies.

What does Cook's forecast show?

Erin Covey, a Cook analyst, framed the shift against a record ad environment. Political spending reached $1 billion in September — the largest September of the past three cycles, per AdImpact, an ad-tracking platform. Republicans drove 60% of that total. Of $1.1 billion booked for October and November, the GOP's share runs about 56%.

"With less than four weeks to go, that heavy spending has yet to move the needle," Covey said.

Cook's October revisions will test whether raw ad volume alone can move numbers.

Why are Iowa's ag districts moving?

Three Iowa races shifted. Tariffs, beef imports and PAC money anchor each one.

• Iowa's 1st District. GOP Rep. Mariannette Miller-Meeks faces Democrat Christina Bohannan. Moved from "Toss Up" to "Lean Democrat." Trade policy dominates ad buys. "Democrats' ads are focused on Miller-Meeks' support for tariffs, which have uniquely harmed Iowa's agriculture-heavy economy, and her support from corporate PACs," Covey said. Miller-Meeks counters with attacks on Bohannan's statehouse record on crime.
• Iowa's 3rd District (Des Moines). GOP Rep. Zach Nunn faces Democrat Sarah Trone Garriott. Moved from "Toss Up" to "Lean Democrat." Over the past month, Nunn voted for a war-powers resolution and introduced a bill to block beef imports — moves to distance himself from President Donald Trump. Democrats hit him on corporate PAC ties and accused him of taking funds from Chinese-owned companies.
• Iowa's 2nd District (Cedar Rapids). Open seat. Democrat Lindsay James takes on former GOP state Rep. Joe Mitchell. Moved from "Lean Republican" to "Toss Up." Trump carried the district by 10 points previously. "This no longer looks like a race where the GOP has a clear edge, even in a district that Trump won by 10 points," Covey said.

The current 2nd District holder, GOP Rep. Ashley Hinson, runs for the Senate seat vacated by retiring Republican Sen. Joni Ernst. Some district polls show Democrat Josh Turek leading Hinson at home, Covey noted.

Trade exposure is reshaping the Iowa map.

What about other ag-touching seats?

Michigan's 4th District moved from "Lean Republican" to "Toss Up." Polling ties GOP Rep. Bill Huizenga with Democrat Sean McCann.

North Carolina's 1st District, held by Democratic Rep. Don Davis, moved from "Lean Republican" to "Toss Up." Redistricting last year redrew the seat. "The seat was redistricted last year, and so it is quite a tough seat for a Democrat to hold," Covey said in a North American Agricultural Journalists webinar. "But due to the environment and due to Davis's own strength as an incumbent, that one is competitive."

Covey also flagged Wisconsin's 3rd District, where GOP Rep. Derrick Van Orden faces Democrat Rebecca Cooke at "Toss Up" since April. California's 22nd District, with GOP Rep. David Valadao facing Randy Villegas, has held a "Toss Up" rating since last November.

Rural districts are doing the lifting.

What changes before Election Day?

Five weeks remain. Cook's next update could redraw districts again if the booked $1.1 billion — most from GOP committees — finally dents Democratic gains across farm-belt turf.