For the last decade or two, the Big Three network news ratings have declined and their once-iron grip on public opinion has loosened, prompting this debate: is this decline merely a sign of increasing 24-7 media availability (cable news, Internet sites) or is the liberal tilt of the networks driving conservative viewers away from these networks in favor of alternative outlets?

Network news executives have consistently chosen the former, denying a liberal bias and denying that the ratings decline means they should have to change their modus operandi in any way. They are in denial of the obvious. A new study by the Pew Research Center for the People and the Press proves the point. It shows a dramatic decline in nightly network news viewership in the last four years among the Republican viewers they polled. While the number of Democrats saying they regularly watch network news increased from 35 percent in 2002 to 38 percent in 2006, the number of Republicans who say they view major TV newscasts declined from 34 percent in 2002 to 24 percent in 2006.

So the evening-news gap is now 14 points, nearly three times as large as it was in 2004: 38 percent of Democrats to 24 percent of Republicans. That noise you hear is the millions of conservatives changing the channel.

Another study might explain some of this exodus. The nonpartisan Center for Media and Public Affairs has studied the positive vs. negative coverage of President Bush in parts of the last four years and found the networks absolutely pound Bush with negative press. In measuring on-air evaluations by nonpartisan sources, the overall tone was 69 percent negative in 2003. Bush's campaign for re-election drove the negative percentage down slightly to 63 percent negative in 2004. If you think that was skewed, get this: it was 79 percent negative coverage in 2005, and 76 percent negative in 2006.

One obvious rebuttal attempt is to drag out the Bad News Defense: clearly, you can't expect Bush to get positive press in a negative time. But consider that CMPA did a similar study in the first part of 1998, when the networks were allegedly scouring President Clinton over the Monica Lewinsky scandal. Clinton's network coverage was only 56 percent negative...while special prosecutor Ken Starr's evaluations were 74 percent negative.

Democrats decry Fox News Channel as GOP-TV, and liberals have a special loathing for "The O'Reilly Factor," with Pew finding 16 percent of Republicans watch it regularly, compared to just 5 percent of Democrats. It doesn't matter how conservative Bill O'Reilly is - or isn't - on any given night. Liberals regularly criticize Fox as a partisan news operation catering to a GOP-leaning audience.

But notice how Pew also found that nearly twice as many Democrats as Republicans (7 percent vs. 4 percent) are regular viewers of PBS's "News Hour with Jim Lehrer," and 22 percent of Democrats listen regularly to NPR, but only 13 percent of Republicans. Democrats also outnumber Republicans among regular viewers of Comedy Central's "Daily Show" with Jon Stewart (by 10 percent to 3 percent). Shouldn't then the conventional wisdom also embrace that these programs can be identified as liberal since they are more passionately embraced by the Left?

In recent years, media elites have worried about partisan polarization, that media consumers on both sides would pursue only the media sources that reinforced their opinions. There's some truth here and viewers ought to be strong enough to hear a different opinion. On the other hand, there's no reason for conservatives to endorse and financially support networks that do nothing but attack them and their ideals and leaders.

A TV news enterprise focused solely on ratings and profits would notice what Pew notices, namely that the TV audience identifies itself as more conservative than liberal. Thirty-six percent identify as conservatives, 35 percent as moderates, and only 21 percent as liberals. Wouldn't it make economic sense to at least proclaim an interest in presenting a "fair and balanced" news menu?

Instead, networks like CBS are offering us Katie Couric touring the country doing her best Hillary Clinton impersonation. They rave about who can be the most emotionally hostile to the White House after hurricanes. Tax cuts only help the greedy rich. Bush is an idiot. Cheney is evil.

They show no signs of really being interested in preventing a further ratings collapse among conservatives. They would rather go down with a sinking ship, pounding their desks and proclaiming the liberal gospel, than consider giving conservatives an even break on the evening news. So be it.

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