Big policy changes seldom occur in a single session of the Minnesota Legislature. More typically, change comes incrementally over several sessions, nudged along by a few key legislators and persistent interest groups who are willing to take what they can get one year and come back again for more.

Second-term Rep. Carly Melin, DFL-Hibbing, is encountering that reality as the sponsor of a bill to legalize the use of marijuana for medical purposes.

On Thursday, Melin stood before TV cameras to announce her decision to limit the scope of her bill, so as to neutralize the opposition of the state's major law enforcement organizations. The new version of the bill will allow cannabis extracts and oils to be prescribed under clinical trials to treat certain medical conditions, and vaporized marijuana to be used under medical supervision.

That's very similar to a proposal Gov. Mark Dayton offered six weeks ago. Melin and medical marijuana advocates rejected it then, saying it did not go far enough. Some advocates say they won't support the new version. They note that a stronger bill, legalizing pot smoking for medicinal purposes, is advancing in the state Senate, and would provide relief for more conditions more conveniently. 

But Melin, a 28-year-old attorney, sounded like a veteran when she explained why she's come around: "I personally wish we could do more. I don't like that some people are being left out. But if we can do something for some people -- and I'm actually of the opinion that this is doing a lot for a lot of people -- then that's actually a pretty big victory for the cause and for a lot of these families. It will allow them to access the medicine they need."

After weeks of trying to persuade medical marijuana opponents that her bill would not erode public health or safety, Melin's persuasive work is not over. She must now convince her allies that doing something beats doing nothing this year. That, too, is the mark of a good legislator.