This week's Mainstream Media Scream looks at the bottom line in the coverage of the Democratic and Republican presidential nominating conventions, and finds that the GOP confab was declared negative and nasty by a 12 to 1 margin.

Mainstream media pulled no punches in slamming the Republicans. Some that featured Democrats on air slamming Republican speeches during the GOP convention refused to put on Republicans to critique the Democratic speakers.

"Every four years, the party conventions give the establishment news media a chance to provide even-handed coverage of the two parties. Once again, unfortunately, the networks have shown their obvious bias in favor of the liberals that rule the Democratic Party," said Rich Noyes, research director at the Media Research Center which helps Secrets ferret out the worst cases of liberal media bias.

Typically we feature one single pick for your weekly Mainstream Media Scream feature, but Noyes produced a very notable and comprehensive wrap-up of the two weeks of political conventions that displays in black and white the disparity in coverage.

For example, ABC, CBS, NBC, CNN and MSNBC slammed the GOP convention as more negative than the Democratic gathering 63-5.

Also, Republican critics of Democratic speeches were missing in action. MSNBC, for example, featured five Democrats commenting on Republicans during primetime but barred Republicans from primetime during the Democratic convention.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com