General Discussion

Janet Mills main problem was being a stop gap solution to the perceived problems with Platner.
As usual Democratic leadership panicked and fell back on the "favorite son" idea for a candidate.
So Mills was the anti Platner. As such she had to attack Platner from the right and she couldn't develop a meaningful platform beyond, I'm experienced, I'm moderate, and I'm not him.

Mills was forced into a role that was never going to win. She had to cede the left to Platner and he ran with it. If we're lucky he'll run right into the senate with it.

This whole problem is caused by the Democratic leadership's love of centrists and fear of criticism.
They should have read the tea leaves and seen that there was a leftist backlash growing. They could have been grooming populist Democrats to run against Collins going back several election cycles.
Instead they get surprised by Platner and fumble.