So, since the former doesn't seem to be used as a human property in its figurative meaning which itself probably doesn't mean exactly what we want, I'm thinking what attributes could Romans give a politician that would mean something at least close. I had few ideas so far...
The word sinceritās (not meaning primarily "sincerity"), according to OLD, means also "straightforwardness" and it is used as a human property. If "truth and straightforwardness" would be an acceptable synonym for the OP, you can use "vēritās sinceritāsque"