House DFLers proposed a state constitutional amendment Thursday that would make it easier to see who is giving money to efforts aiding candidates, the latest twist in an ongoing feud over the disclosure of campaign contributions.

Current law shields certain groups from having to disclose money they raise and spend as long as it is spent on so-called issue-based advertising that does not expressly say "vote for" or "vote against" a candidate.

The DFL says that's a loophole and the proposed amendment would close it, requiring the groups to disclose where they receive the money and how they spend it.

A constitutional amendment would need to pass both houses of the Legislature to appear on the ballot and then be approved by the voters in November.

"It's time for politicians to … give Minnesota voters the opportunity to decide for themselves if they have a right to know who is spending money to influence their vote," said House Minority Leader Paul Thissen, DFL-Minneapolis.

Republicans said the proposal is designed to discourage GOP donors from giving to the groups, fearing their names would be made public.

"This proposal seeks to limit free speech for those who disagree with the DFL and their big-spending special interest friends," said Rep. Tim Sanders, R-Blaine, chairman of the House Government Operations and Elections Policy Committee. "Furthermore, it is unclear how amending the state Constitution would override federal protections of free speech."

Thissen said he thinks now is the right time to bring the issue to the voters.

He said many Democrats were shocked by the volume of money spent in 2014, its true origins sometimes untraceable.

Mailboxes in many districts were flooded with dozens of mail pieces in the weeks leading up to that election, he said.

Both sides are now using newly relaxed campaign finance rules — the result of several U.S. Supreme Court decisions from the past decade or so — to raise more money than ever before and sometimes shield their donors from being revealed.

The proposal faces steep obstacles. It's not clear it would even receive a House or Senate vote when the Legislature convenes March 8. The Republican House majority determines what measures are brought to the House floor, so Sanders' opposition is significant.

J. Patrick Coolican • 651-925-5042