Rep. Rod Blum, an Iowa Republican waging a tough battle for re-election, has spent more on taxpayer-funded mass mailings to constituents than any other House representative.

Blum spent more than $400,000 in taxpayer money on mass mailings and mass communications to his district from January of 2017 through March 31, according to expense records reviewed by the Associated Press.

That’s more than any other House member and far more than the three other Iowa congressmen, who spent less than $20,000 combined.

Blum is locked in a heated re-election fight for a third term in Iowa’s 1st District against Democratic challenger, Iowa state representative Abby Finkenauer. The seat is key for Democrats in their campaign to take the House in 2018. Inside Elections with Nathan L. Gonzalez rates the race a Toss-up.

His mailings were funded by taxpayers thanks to a privilege known as “franking.” The privilege, which dates back to 1775 in the United States, allows all members of Congress to send mail to constituents with simply their signature, on the taxpayers’ dime — no postage required.