A state ballot measure seeking to end political corruption has won the ire of the billionaire Koch Brothers, who have relied on secret donations to conservative interest groups to influence elections coast to coast.

South Dakota's Initiated Measure 22 (pdf), dubbed the Government Accountability and Anti-Corruption Act, seeks to "ensur[e] that special interest lobbyists and their cronies aren't buying influence with our elected officials," according to proponents South Dakotans for Integrity.

Specifically, it calls for public disclosure of donors to campaigns and advocacy groups; lowers contribution amounts and imposes limits on political action committees, political parties, and candidates; and it creates an ethics commission to enforce campaign finance and lobby rules. Further, it establishes a publicly funded campaign finance program for state and legislative candidates.

State residents will have the chance to vote on the measure in November and, apparently, the Koch-backed Americans for Prosperity (AFP) is hoping to quash this effort before it gains traction in South Dakota, or anywhere else.

USA Today's Fredreka Schouten reported Wednesday that an AFP-founded coalition, Defeat 22, has launched an aggressive opposition campaign, which "already has run commercials on talk radio and country-music stations, contacted 50,000 voters through phone calls and door-knocking and distributed mailers denouncing the initiative as a money-grab by politicians."

The Defeat 22 campaign has not yet submitted a campaign finance report, but South Dakotans for Integrity has raised $20,000 from a single group called Represent Us, according to their filing with the South Dakota Secretary of State.

As the Yes on 22 campaign notes, South Dakota scored an F grade (ranking 47 out of 50 states) on the Center for Public Integrity's 2015 state report. The state scored lowest on Political Financing, Lobbying Disclosure, and Ethics Enforcement Agencies, among others, which makes it an ideal market for the fossil fuel giants to peddle their influence.

In a recent letter published in the Argus Leader, Yankton resident Chris Svarstad wrote, "the out-of-state oil and tar sand billionaires, Charles and David Koch, are trying to buy South Dakota's future."