JEFFERSON CITY, Mo. (AP) — The group fighting a ballot measure that would make Missouri a right-to-work state has outraised its opponents by more than $4 million.

Formed last year in Jefferson City, We Are Missouri has raised more than $5.4 million since the beginning of April, according to reports released this week by the Missouri Ethics Commission. Most of the largest donations came from unions both within and outside of the state.

In contrast, the three groups campaigning in favor of right-to-work pulled in more than $1.2 million. The largest donation of half-a-million dollars came from A New Missouri, the nonprofit recently accused in an ethics complaint of violating campaign finance laws while essentially functioning as an unofficial arm of former Gov. Eric Greitens’ operation. A New Missouri can shield its donors’ identities, so the ultimate source of the money is not known.

A lawyer representing A New Missouri has denied criminal wrongdoing.

The fundraising disparity could certainly impact the Aug. 7 election, said University of Missouri-Columbia political scientist Peverill Squire.

“Just being able to get that information out and make their argument probably will help mobilize voters and maybe convince a few people that the opposition’s the correct one,” Squire said.

Prohibiting mandatory union fees in the workplace had long been a priority of the Republican-led Legislature, but it wasn’t until they had a Republican executive in Greitens that GOP lawmakers were finally able to pass a right-to-work law.

That measure was put on hold, however, after a union-backed effort gathered enough signatures to put the question before voters.

The election was originally scheduled for the November midterms, but during the last legislative session lawmakers moved the ballot question to August, saying businesses needed to know as soon as possible whether the law would ultimately take effect.

We Are Missouri, which wants to overturn that law, spent more than $6.8 million last quarter. Millions went to advertisements, and the group still had more than $3.7 million on hand at the end of June.

That’s more than triple of what remains with its three similarly named opponents.

Missourians For Freedom To Work, formed April in Union, pulled in a little less than $600,000 during the last quarter. Freedom To Work, formed last year in Excelsior Springs, received more than half-a-million dollars. Missourians For Worker Freedom, formed 2016 in Kansas City, brought in an even $5,000.

Those numbers stemmed from around a dozen large donations. In addition to A New Missouri, money came from Joplin-based donor David Humphreys and the Missouri Chamber of Commerce and Industry.

During the same period the three groups spent more than $2 million on mostly behind-the-scenes work that included focus groups and an aborted effort to gather signatures for a rival ballot initiative.

All together, they had just under $1 million on hand at the end of June, but that number didn’t include an additional $100,000 one of the groups received at the beginning of July for the final three weeks of the campaign.

The reported funds include in-kind contributions.

On the ballot, voters will be asked if they want to adopt “Senate Bill 19.” Voting “yes” will ban mandatory union fees. Voting “no” will overturn the right-to-work law.