Being the New York Times: the political behaviour of a newspaper

I analyze a dataset of news from the New York Times, from 1946 to 1997. Controlling for the incumbent President's activity across issues, I find that during the presidential campaign the New York Times gives more emphasis to topics that are owned by the Democratic party (civil rights, health care, labor and social welfare), when the incumbent President is a Republican. This is consistent with the hypothesis that the New York Times has a Democratic partisanship, with some "watchdog" aspects, in that -during the presidential campaign- it gives more emphasis to issues over which the (Republican) incumbent is weak. In the post-1960 period the Times displays a more symmetric type of watchdog behaviour, just because during presidential campaigns it gives more more coverage to the typically Republican issue of Defense when the incumbent President is a Democrat, and less so when the incumbent is a Republican.