This article has been revised to reflect the following correction: This story was updated to clarify the group’s goal. 

PIERRE, S.D. (KELO) — A national group pushing for a convention of states to amend the U.S. Constitution has spent quite a bit this spring trying to replace a handful of South Dakota Republican legislators.

Convention of States has filed independent expenditure reports opposing the re-election of incumbent senators Lee Schoenbeck of Watertown, Mary Duvall of Pierre and David Johnson of Rapid City, as well as Representative Tim Reed of Brookings, who’s running for the Senate.

The Houston, Texas-based organization is supporting instead their opponents in the June 7 Republican primary elections: Colin Alan Paulsen of Watertown, Jim Mehlhaff of Pierre, Janet Jensen of Rapid City and Julie Erickson of Brookings.

House Joint Resolution 5001 calling for South Dakota to join the list of states that officially support holding a U.S. national convention passed the House of Representatives 39-30 this year, with Reed voting against it.

When the resolution crossed to the Senate for a second committee hearing, Schoenbeck and Duvall voted against it. They and Johnson then voted against it during a failed attempt to force it onto the Senate debate calendar.

Duvall, Johnson and Reed voted against similar resolutions in past years. Schoenbeck is Senate president pro tem, the chamber’s top member.

So far this election, Convention of States has reported spending about $208,000 against the four incumbents on mailers, ads and polling, while spending more than $21,000 in support of their four challengers.