Pendragon, I (think) I have completed the grid, but I have been working on a completely different wavelength to you, by the examples you quote, if I am correct. I may not be correct because I can't see the politician or make sense of the extra letters fore the quotation, one of which is a Z.
My solutions involve removing an extraneous letter in the cryptic part of 27 clues (though two of mine are doubtful). The remaining 8 clues have their definition parts swapped round, and are paired.
Am I correct?
And could somebody offer me a clue as to how to spot the politician?