These newspapers are insiders. My sense is that their endorsement is utilitarian. If Obama were ahead, they’d be endorsing him.
I wonder if their insider position gives them access to internal polling? If so, this kind of endorsement says that Romney is ahead.
I call these papers endorsing Romney as inocculating themselves. They will begin viciously attacking Romney about a week after his inauguration, and when people call them on it, they will say “But we endorsed him”.