JEFFERSON CITY • A long-running effort to end the era of megadonors in Missouri elections is again being challenged in federal court.

In a lawsuit filed Wednesday morning, the same group that unsuccessfully sought to block a statewide referendum on contributions before the Nov. 8 election argues that the change in the Constitution approved by voters unfairly limits some businesses and associations from giving money to campaigns.

In particular, the change approved by voters would stop the Association of Missouri Electrical Cooperatives from donating to campaigns and political action committees, violating the free speech rights of its members, the lawsuit notes.

The legal action came one day before the new limits were set to kick in after 70 percent of the voters last month said they favored restoring limits.

Under the constitutional change, contributions to individual candidates would be limited to $2,600 per election, while contributions to a political party would be capped at $25,000.

The change also attempted to ban the current practice of funneling money through different committees to hide the source of the contributions. It prohibits contributions by foreign interests and companies not legally authorized to conduct business in Missouri.

Missouri had campaign limits until the Legislature removed them in 2008. Since then, six- and seven-figure contributions have become commonplace. On Tuesday, for example, Sen. Dan Brown, R-Rolla, gave $200,000 to his son, Justin, who is prepping for a 2018 bid for his father’s seat.

Jefferson City attorney Chuck Hatfield said the electrical cooperative organization doesn’t oppose the limits. Rather, he said, the group doesn’t want to be barred from participating in the electoral process while others are allowed to continue.

Before the election, an appeals court stopped a previous lawsuit from moving forward, saying the legality of campaign limits could not be decided until the limits actually go into place.

The Missouri Ethics Commission announced on Dec. 1 that the limits would go into effect Dec. 8. In addition, the commission, which regulates campaign giving, said candidates in local races are not affected by the constitutional change.

That means there are no caps on donations to candidates running for mayor of St. Louis or in other nonstate races.

The lawsuit was filed in U.S. District Court in St. Louis.