AP:

The fliers piled up in mailboxes in central South Dakota like snow during a high-plains blizzard: “Transgender Sex Education in Schools?” one asked. “Vote Against Sex Ed Radical Mary Duvall for State Senate.”

The mailers were part of a $58,000 campaign against the five-term Republican lawmaker, an enormous sum of money in a place where the cost of running for a statehouse seat is typically in the low five figures. Despite the subject of the attack ads, Duvall was targeted not for her stance on sex education but for her opposition to a longshot bid by some conservatives to force a convention to amend the U.S. Constitution.

“I knew they were angry at me, but I had no idea this was going to be coming during my primary campaign,” said Duvall, who ended up losing her race by 176 votes.

Duvall opposed legislation that would have added South Dakota to 19 other states calling for a gathering known as a convention of states, following a plan mapped out by a conservative group that wants to change parts of the United States’ foundational document. When that number hits two-thirds of the states — or 34 — under the procedure laid out in the Constitution, a convention would meet with the power to amend the 235-year-old document.

The campaign against Duvall was part of a more than $600,000 push in at least five states earlier this year by the group, Convention of States Action, and its affiliates in Republican primaries to elect sympathetic lawmakers who could add more states to its column. Much of the money comes from groups that do not have to disclose their donors, masking the identity of who is funding the push to change the Constitution.

Mark Meckler, the group’s president and former head of Tea Party Patriots, issued a brief statement saying the group was committed to being active in the midterms “in a big way.”

For years, Convention of States Action has been a staple of the conservative political scene. But its engagement in primary campaigns marks an escalation at a time when parts of the conservative movement are testing the limits of the nation’s political rulebook, pushing aggressive tactics from gerrymandering to voting restrictions.