Republicans are dramatically boosting Senate spending in Ohio and Iowa to shore up seats that only months ago looked safely out of Democrats' reach, according to reservation plans obtained by Axios.

One Nation, the conservative nonprofit aligned with Senate Majority Leader John Thune, R-S.D., is reserving $28 million in TV advertising in Ohio and $11 million in Iowa, with spots beginning Wednesday and running through the summer.

The move reflects growing GOP unease about defending two states President Donald Trump carried by double digits in 2024.

Sen. Jon Husted, R-Ohio, is locked in a close race against former Democrat Sen. Sherrod Brown, who has outraised him by more than 2-to-1, hauling in $12.5 million in the first quarter to Husted's $2.9 million.

Cook Political Report has rated the special election a toss-up.

In Iowa, Rep. Ashley Hinson, R-Iowa, is confronting voters unhappy with Trump's tariffs and a struggling farm economy.

She faces state Rep. Josh Turek, a Paralympic wheelchair basketball medalist who is hammering Trump's policies on working families.

National Democrats have already booked a $13.4 million ad reservation targeting Hinson.

The new commitments follow a June 1 conference call in which One Nation Executive Director Alex Latcham urged Thune and top GOP donors to double down on GOP-held seats in Ohio, Iowa, Alaska, Maine, and North Carolina.

Latcham also touted roughly $100 million in planned spending against Democrat-held seats in New Hampshire, Georgia, and Michigan.

The Senate Leadership Fund, the SLF super PAC allied with One Nation, has separately unveiled a $342 million eight-state plan that puts $79 million behind Husted, its largest single commitment.

One Nation is also reserving $6 million in New Hampshire, where retiring Democrat Sen. Jeanne Shaheen's seat is up for election, and Democrat Rep. Chris Pappas is expected to face former Republican Sen. John Sununu.

Democrats need a net gain of four seats to flip the chamber.

Their path narrows sharply if Republican Sen. Susan Collins survives in Maine and the GOP holds Ohio and Iowa. Maine Democrats' nominee, Graham Platner, is facing calls to withdraw over sexual misconduct allegations, which he has denied.

"One Nation is proud to highlight the many conservative policies that have provided meaningful results for working families," Latcham said in a statement.

Democratic Senatorial Campaign Committee spokesperson Tommy Garcia countered that the spending shows Republicans "know just how fragile their Senate majority is."