In the course of thinking about a St. Pat's Day parade, it occurred to me to consider how I would do such a thing, here. Likely, I'd start with a vulnerable local politician, and suggest that this would get him a lot of publicity, but certainly help me decide, come voting time. So it wouldn't just be my voice, I'd have the local car clubs badger him, as well as the food truck people. I'd indicate to some local bands that the politician was looking for some good musicians, then give them his number.
I'd contact the health & fitness people, and advise them that they should support the politician's efforts to get people outdoors.
There are some local veterans groups, so I'd let slip the possibility that the politician might not let them participate, unless they spoke up soon.
There are a bunch of businesses on what amounts to Main St. I'd let them know this was coming, and advise them of possible revenue opportunities, if the mayor could pull this off.
I'd pick 2 political adveraries to lead the parade, but only tell them about the other if they refused to participate.
I'd find some activist group to fund the activity, but accidentally direct them to a different locale.
If that didn't get things rolling, I'd likely have a bunch of flyers circulated, advertising the event, crediting whichever politician would seem to be the most effective.