Newspaper endorsements roll in for Obama

Several nationally prestigious newspapers have recently announced their endorsement for Democratic candidate Barack Obama, including the Washington Post, Los Angeles Times, and Chicago Tribune. It is the first time the Tribune, since its founding in 1847, has ever endorsed a Democratic candidate. In its endorsement, the Chicago Tribune writes:

It may have seemed audacious for Obama to start his campaign in Springfield, invoking Lincoln. We think, given the opportunity to hold this nation's most powerful office, he will prove it wasn't so audacious after all. We are proud to add Barack Obama's name to Lincoln's in the list of people the Tribune has endorsed for president of the United States.

According to Editor and Publisher, Obama holds a 3-1 lead to McCain in newspaper endorsements, a much more significant lead than Kerry held over Bush in 2004. Will these endorsements have an effect on public opinion, or are they simply reflective of the recent polls?