A suggestion, if others agree it might work, would be to use multiple boards. The main one with big fonts and catchy slogans to attract attention. And add one with easily proved broken electoral promises that screwed over his voters already.

Also, I’d say to be prepared to give examples that need no deep explanations and/or where to find out for themselves. Leading people into researching on their own should work better than explaining it to them directly?

Anyway, good luck and remember to care for yourself.