There may be no more powerful editorial tool than the cartoonist’s pen, and a sharp-eyed reader can trace the political fortunes of those in the public eye by observing the way in which they are depicted by those merciless caricaturists. A new exhibit in London examines just such a progression by displaying British cartoonists’ visions of Prime Minister Tony Blair over the course of his career at the top of the Labour Party. “A decade ago, cartoonists emphasized Blair’s broad smile, intense gaze and large ears. But over the years they have become crueler — and funnier — as Blair himself has changed.”