JEFFERSON CITY, Mo. (AP) — Two nonprofits have donated hundreds of thousands of dollars to political action committees working to protect a Missouri right-to-work law that takes effect this month.

The Kansas City Star reports American Democracy Alliance contributed $350,000 to a PAC called Liberty Alliance and $150,000 to another PAC called Missourians for Worker Freedom.

Republican Gov. Eric Greitens’ nonprofit called A New Missouri Inc. donated $100,000 to Missourians for Worker Freedom. A New Missouri Inc. last month gave that PAC $250,000.

The nonprofits aren’t required to disclose their donors. When contributions are routed through a nonprofit to a political campaign to hide the donation’s source, it’s called “dark money.”

The contributions seek to stave off a union-backed effort to put the right-to-work law Greitens signed in February on the 2018 ballot.