Noting that "a multitude of information sources" exist today besides it (read: online journalism), the Chicago Sun-Times seems to acknowledge its and other newspapers' waning influence as why it has decided to quit endorsing candidates for office. Yes, the editorial from the newspaper today cites the desire to let readers make up their own minds and the need to appear impartial as reasons why the Sun-Times is removing itself from the political endorsement business at all levels of government, for 2012 and beyond. But the main reason the newspaper strangely (and tellingly) gives as to why its political endorsements are no longer merited is the fact that newspapers are no longer all that influential. As the Sun-Times puts it: 

What we will not do is endorse candidates. We have come to doubt the value of candidate endorsements by this newspaper or any newspaper, especially in a day when a multitude of information sources allow even a casual voter to be better informed than ever before.

Research on the matter suggests that editorial endorsements don’t change many votes, especially in higher-profile races.

It's a (somewhat depressing) acknowledgement of something readers, who vote for who they want regardless of who their favorite daily endorsed, already knew. The Sun-Times, though, is not the only newspaper to refrain from endorsing as a matter of policy, though with a circulation for 419,407 (tenth in the country) it's certainly one of the biggest. USA Today and The Wall Street Journal generally don't endorse candidates for president, for example -- though The Journal came close in 2008.