Despite months of pressure by Democrats and outside groups, the fight in Washington over filling a vacancy on the Supreme Court is having little impact on Sen. Chuck Grassley’s (R-Iowa) reelection campaign, according to a new poll from a GOP firm.

The North Star Opinion Research survey found that just 9 percent of all Iowa voters ranked the Supreme Court as one of the top three issues that will determine how they vote in November. Grassley, the Senate Judiciary Committee chairman, has been at the forefront of the GOP’s refusal to give President Obama’s nominee, Merrick Garland, a hearing or a vote.

“Voters know little about Merrick Garland personally, and are not following the issue particularly closely. Moreover, the debate is not hurting Senator Chuck Grassley, who is in a solid position as he begins his reelection campaign,” Whit Ayres, the president of North Star Opinion Research; and Dan Judy and John McHenry, vice presidents of the GOP consulting firm, wrote in a memo obtained by The Hill.

Overall, 47 percent of Iowa voters would prefer the next president to fill the late Justice Antonin Scalia’s seat, and 45 percent want it filled immediately. Among Republicans, 77 percent want the seat to remain vacant until 2017.

The firm conducted a survey of 500 registered Iowa voters from May 17–19. The survey was commissioned by the Judicial Crisis Network, a conservative group that has vocally opposed Garland’s nomination.

Carrie Severino, the chief counsel for the Judicial Crisis Network, said the survey “confirms that Iowans are on their side.”

“Senator McConnell and Senator Grassley stood on principle in rejecting Garland’s nomination,” she added. “Democrats have wasted millions of dollars on advertising, PR stunts and astro-turf activity, and if I were one of their donors I would be asking for my money back.”

Democrats and a cadre of outside groups have made Grassley a top target in their attempts to force Republicans to take up Garland’s nomination.

Senate Minority Leader Harry Reid (D-Nev.) has repeatedly knocked Grassley and GOP leadership over the Supreme Court fight, arguing that they want presumptive GOP presidential nominee Donald Trump to fill the vacancy.