The center reviews and "codes" statements on the evening news as positive or negative toward the candidates. For example, when NBC reporter Andrea Mitchell said in June that Obama "has problems" with white men and suburban women, the media center deemed that a negative.
The positive and negative remarks about each candidate are then totaled to calculate the percentages that cut for and against them.
Visual images and other more subjective cues are not assessed. But the tracking applies a measure of analytical rigor to a field rife with seat-of-the-pants fulminations.
The media center's most recent batch of data covers nightly newscasts beginning June 8, the day after Hillary Rodham Clinton conceded the Democratic nomination, ushering in the start of the general-election campaign. The data ran through Monday, as Obama began his overseas trip.
Most on-air statements during that time could not be classified as positive or negative, Lichter said. The study found, on average, less than two opinion statements per night on the candidates on all three networks combined -- not exactly embracing or pummeling Obama or McCain. But when a point of view did emerge, it tended to tilt against Obama.
That was a reversal of the trend during the primaries, when the same researchers found that 64% of statements about Obama -- new to the political spotlight -- were positive, but just 43% of statements about McCain were positive.
Such reversals are nothing new in national politics, as reporters tend to warm up to newcomers, then turn increasingly critical when such candidates emerge as front-runners.
It might be tempting to discount the latest findings by Lichter's researchers. But this guy is anything but a liberal toady.
In 2006, conservative cable showmen Glenn Beck and Bill O'Reilly had Lichter, a onetime Fox News contributor, on their programs. They heralded his findings in the congressional midterm election: that the networks were giving far more positive coverage to the Democrats.
More proof of the liberal domination of the media, Beck and O'Reilly declared.
Now the same researchers have found something less palatable to those conspiracy theorists.
But don't expect cable talking heads to end their trashing of the networks.
Repeated assertions that the networks are in the tank for Democrats represent not only an article of faith on Fox, but a crucial piece of branding. On Thursday night, O'Reilly and his trusty lieutenant Bernard Goldberg worked themselves into righteous indignation -- again -- about the liberal bias they knew was lurking.
