CORALVILLE, Iowa — Election seasons in this small eastern Iowa town are usually cordial affairs. But this year, a group backed by the billionaire Koch brothers has changed that.

The group, Americans for Prosperity, has jumped into the race to elect Coralville’s next mayor and City Council with an aggressive campaign, mailing fliers, advertising in newspapers, calling voters and knocking on their doors. Its latest leaflet hit mailboxes last week, denouncing the town’s growing debt and comparing it to the financial woes of Detroit. “Coralville is fast becoming Iowa’s version of Detroit,” it read.

Tuesday’s race here is not the only one that has drawn the interest of Americans for Prosperity, which was founded by Charles and David Koch. Local chapters have been involved in property tax fights in Kansas, Ohio and Texas, the group says.

In January, the group successfully fought an increase in a food and beverage tax in Fremont, Neb. And last spring, it opposed a tax increase in Gahanna, in central Ohio. Voters rejected the tax measure in May, but the City Council has put it back on Tuesday’s ballot.