Megan McArdle had a post a few days ago touching on Murdoch’s influence in Britain, saying “As far as I know, studies of media bias generally find that the political slant of newspapers tracks the politics of their readership; the New York Times is not visibly left-leaning because its reporters are fooling the folks on the Upper West Side, as conservatives complain, but because the folks on the Upper West Side demand news sources that agree with them”. It would be great if we had an experiment where an exogenous change occurs in a newspaper’s political support. And John Sides at the Monkey Cage says that’s basically what happened when some British papers switched to supporting Labour in 1997.