Do print media significantly impact political attitudes and party identification? To examine this question, we draw on a rare quasi-natural experiment that occurred when The Sun, a right-leaning UK tabloid, shifted its support to the Labour party in 1997 and back to the Conservative party in 2010. We compared changes in party identification and political attitudes among Sun readers with non-readers and other newspaper readerships. We find that The Sun’s endorsements were associated with a significant increase in readers’ support for Labour in 1997, approximately 525,000 votes, and its switch back was associated with about 550,000 extra votes for the Conservatives in 2010. Although we observed changes in readers’ party preference, there was no effect on underlying political preferences. The magnitude of these changes, about 2% of the popular vote, would have been unable to alter the outcome of the 1997 General Election, but may have affected the 2010 Election.