ST. PAUL  — A House committee defeated a bill Thursday that would have forced some groups active in Minnesota politics to disclose more details about their spending late in campaigns.

The setback might not be the final word for advocates because the concept has the backing of key senators and Gov. Mark Dayton, who could attempt to revive it in end-of-session negotiations. There also is a separate House bill recently introduced by majority Republicans that expands campaign disclosure laws but in a more limited way.

The 8-6 vote in the House Government Operations and Elections Policy Committee fell along party lines in the Republican-led panel. Democratic Rep. Ryan Winkler told members before the vote to bring more sunlight to campaign spending.

“Corruption feeds on secrecy and darkness,” he said.

The debate follows a 2014 campaign where independent groups flooded mailboxes with issue advocacy pieces in swing districts that didn’t fall within existing disclosure laws. They didn’t count as typical campaign spending because they omitted key words urging people to vote for or against a candidate.

Winkler’s bill wouldn’t have stopped the mailings or broadcast ads but would have required the senders to shed light on donors if the ads were done within 30 days of a primary or 60 days of a general election.

John Knapp, a lobbyist for the Minnesota Business Partnership, said the bill would make “an unfair and unbalanced system for political speech even more unbalanced.” He said it would turn a subjective test for deciphering electioneering from issue advocacy into a subjective test.

Republican Rep. Jim Nash raised doubts that the proposed law would survive legal scrutiny on constitutional free speech grounds.