Dems don't need to advertise. They are being overwhelmed by interested candidates at every level of office.
Off the top of my head, Dems are currently facing a recruitment problem in NV-GOV,, WI-GOV, MA-GOV, AZ-SEN...
Problem with MA, is that nobody wants to waste their energy fighting Baker. He's very popular here, and has distanced himself far far away from Trump. MA has Joe Kennedy III as a sort of young star, and I'm glad he didn't run against Baker because he'd probably get put into the ground.
This is silly; Massachusetts is a sufficiently Democratic state (and sufficiently the right sort of Democrat) that anti-Trump backlash could still kill Baker, and even if it doesn't the statewide exposure from a gubernatorial run could be very useful in a future attempt.
Which is why you already have people like Setti Warren or Joe Avellone preparing to enter, and Jay Gonzalez already declared. These guys are B- and C-listers, but the Democratic gubernatorial nomination against Baker in 2018 is a prize worth having for a B- or C-lister.