The more interesting question to me is how helpful, and whether they’re a good idea. Tim Porter, in AJR in 2004, noted:
They have some value to some people some of the time in some circumstances, but no one can say how much to whom and when–for sure.
Research suggests that newspaper endorsements have only a slight impact on election results. From 1940 to 2002, newspaper endorsements changed perhaps 1 percentage point of the vote, according to a 2004 study by Steve Ansolabehere, a political science professor at the Massachusetts Institute of Technology. Kathleen Hall Jamieson, former dean of and now a professor at the Annenberg School for Communication at the University of Pennsylvania, has studied the issue over time and found that “the more visible the race, the less impact the endorsement has.”
Dean Jamieson, again, on the NewsHour in 04:
Kathleen Hall Jamieson… noted that endorsements are less important to readers than they are for the campaigns, which often use them as proof of their superiority over their rival. “The effect of the editorials doesn’t come out of people reading them, they come out of the ads by the candidates saying ‘I’ve been endorsed,'” Jamieson recently told UPI.