Mike Wittenwyler, a Madison attorney who specializes in campaign finance issues and who has represented outside political groups, said the law changes were “long overdue.” The last major rewrite was in the 1970s, he said, prior to several key court decisions that clarified the limits and rights of donors and candidates.

A Marquette Law School poll found that most citizens of Wisconsin disagreed with the Legislature’s 2015 decision to remove contribution limits on state political parties. In a poll, 61 percent of respondents said they opposed unlimited contributions, while 13 percent supported them. Another 25 percent said they had not heard enough on the issue.

Taken together, these changes have made Wisconsin the “darkest of dark money states,” said Jay Heck, executive director of the Common Cause in Wisconsin, which promotes clean, open and responsive state government.

Matt Rothschild, executive director of the Wisconsin Democracy Campaign, another good government group, offers a similar assessment. “Wisconsin,” he said, “is open for bribery.”

Weiner said secret campaign contributions can come from interests on the left or the right, especially in state elections.