Last week janitors went on strike for one day to call for higher wages for the people who clean most of the downtown Minneapolis and St. Paul office buildings. Before they did, some of them were part of a "unity march" with other groups through downtown Minneapolis at morning rush hour, clogging traffic and backing up cars for miles on freeways entering the city.

This week, Black Lives Matter St. Paul appears ready to interrupt the Crashed Ice event, a mad mouse race on ice skates that brings thousands of people to the city center. It will be the last of several instances where the group has chosen to use disruption to bring attention to its issues.

Inevitably, questions arise as to whether such disruptive protests help or hinder the cause. Do they empower, or turn off, potential sympathizers?

BLM St. Paul had a list of demands, chief among them the removal of St. Paul police Sgt. Jeffrey Rothecker, who admitted to telling people on Facebook that they should run over protesters. Rothecker resigned last week, and some people gave the group credit for forcing the resignation.

I doubt Rothecker would agree. More likely, he quit because the investigation was coming to a close and he knew he was going to be fired anyway. By resigning, Rothecker was able to keep the results of the investigation out of the public view.

BLM leaders have said they still intend to proceed with the action at Crashed Ice, citing other demands that have not been fulfilled. Some of those demands, such as taking away Rothecker's pension, are not even possible. He contributed to the pension throughout his career; it's essentially his money.

Another of the BLM demands, elimination of the progressive discipline policy that allows for increasingly harsh penalties for each officer violation, would not change the fact that police chiefs can, and do, fire officers for egregious first offenses.

Still other demands, such as investigating all of the officer's arrests, can't be met before Crashed Ice begins.

Jack Nelson-Pallmeyer, a professor of justice and peace studies at the University of St. Thomas who studies protest and civil disobedience, said that these protests are "aimed at the idea that the only way to make change is to disrupt. It's building on the idea that things they have done in the past have not worked. I'm really intrigued by the tactic; it can work, but it's risky," he said.

In the case of BLM and Rothecker, "sometimes you have to know when to claim success and move on," Nelson-Pallmeyer said.

Richard Keiser, a political science professor at Carleton College, defends bringing the issue to the event because venues for disagreeing with the government have dwindled.

"The public square for commerce and promenading has been replaced by privatized spaces like malls," Keiser said in an e-mail. "Between the privatization of public spaces and the regulation of downtown streets and sidewalks, protesters can too easily be herded out of sight and therefore out of mind."

As for BLM making demands unlikely to be met, Keiser wrote that "politics is the art of the possible. When political actors are successful, compromises emerge and actors on all sides get some of what they want in exchange for ceding ground on other issues. So a list of demands should always include things that seem more likely and some that seem less likely, less likely at least for the present. … Perhaps if black lives mattered as much as entertainment and tourism dollars (which is what the Crashed Ice event is about), politicians would be quicker to discern the art of the possible."

Nelson-Pallmeyer said the one-day strike by the janitors can be very effective because "inconveniencing your employer sends a message that you are willing to do it for the long term."

Holding up traffic, however, may backfire.

"There is a bigger campaign out there to raise wages," he said. "You have to care about what the public thinks. In the long run, you need a lot of public support. If they had asked me, I would have discouraged (blocking traffic) in this case. I didn't see a way that it achieves your long term goal."

In general, Nelson-Pallmeyer says protesters should "try to look at who has the decisionmaking ability to meet your demands. If a tactic is geared to that, it can work."

Nelson-Pallmeyer said disruptive actions by BLM may have prompted Gov. Dayton and some legislators to consider a special legislative session to address inequity.

Keiser said alienating tepid sympathizers should not be a chief concern.

"Political scientists like to … measure the salience of goals," he said. "Perhaps making clear the salience of the issue for those affected may be the best way to get other citizens to change their cost-benefit analysis."

We may find out this weekend if BLM can show the salience of its issues and alter the cost-benefit analysis of thousands of extreme sports fans fueled by energy drinks and liquor.

What could possibly go wrong?

jtevlin@startribune.com • 612-673-1702