These statistics lend credence to the belief that yes, Virginia, there is such a thing as a liberal media, Denton says. "This profession tends to attract individuals who think a certain way, who have a particular political orientation."

Denton's second category, conservative bias, seems to be a complete contradiction of the first--although this type has less to do with the reporters of the news than with the companies running the news organizations. Media owners and corporate leaders tend to be conservative and focused on the bottom line, Denton says--and they can influence editorial content.

In late May, CNN reporter Jessica Yellin revealed to Anderson Cooper that network executives at her former employer, MSNBC, exercised exactly such editorial influence before the beginning of the Iraq War. "The press corps was under enormous pressure from corporate executives, frankly, to make sure that this was a war presented in a way that was consistent with the patriotic fever in the nation and the president's high approval ratings," Yellin said. She added that these same executives actually edited her pieces and turned down stories critical of the administration in favor of positive ones.

Another facet of conservative bias is the degree of influence that advertisers have over editorial content. In an increasingly challenging fiscal environment for media, particularly for newspapers, editors are slow to offend lucrative sponsors. "Are you going to do a horror story on cars and risk offending, say, a car dealership that pays a lot of money to advertise with you?" Denton asks. He recalls an instance when a southwestern Virginia network ran a story that made a sponsor unhappy--and the station lost $250,000 within a day.

Interestingly, a third member of the liberal-to-conservative spectrum is the belief that there simply is no bias in the media. More than 15 studies conducted between 1968 and 2001 found no bias of any type across all media and contexts, Denton says.

Given the aforementioned types of bias, Denton’s fourth category, coverage bias, seems especially important. This type of bias looks at whether one side is covered more than the other. One way of measuring coverage bias is through content analysis, including how the journalist approaches a story. "For example, an anchor might say, 'Now to the quagmire in Iraq,'" Denton explains. "'Quagmire' is not an objective word; it's making a judgment."

	"Politicians do not like the Internet. Campaigns are all about control, and most campaign people despise the Internet because they can't control it." Denton attributes this to what he calls the "YouTube phenomenon" where, thanks to cell phone photography and videos, "there is no back stage anymore--everything a politician does is made public, 24-7." If a politician makes an offhand, off-color remark or says something ill advised at a political rally, the faux pas stands a far greater chance of being posted to such sites as YouTube and circulated around the world within a matter of minutes.

Coverage bias may not, however, be ideological or partisan. Instead, a media outlet may cover a candidate based on his or her standing in public opinion polls. Several studies have shown that the more the general public appears to favor a candidate, the better the press coverage he or she will receive. There's also the issue of where the story is--this summer, for example, Hilary Clinton and Barack Obama received a lot more coverage than did John McCain. "It was history in the making," Denton notes, "so when you look at this frequency of coverage, you can't ignore the context."

"People are beginning to ask why everybody thinks the media is so biased. Starting with the presidential campaign of 2000, with all of the intensity and division, what people are finding is that what you see depends upon where you come from," Denton says. "So if you're a highly partisan person, you're going to see everything as a bias. If you're a strong Republican, you're going to see the media as liberal. If you're a strong Democrat, you're going to see the media as conservative." He calls this the "hostile media" effect--the more cynical a person is, the higher levels of bias he or she will perceive.

A sixth category comes back to the reporters themselves, which Denton calls inherent process or newsgathering bias. This type, he says, stems from the drastic change in the role of journalism after the Watergate scandal. "The initial idea was that a journalist was simply a conduit: I just report. Objectivity was the standard. And then, post-Watergate, journalists took on a watchdog role, which means that the media is a bit more adversarial now, particularly toward the government."

Denton has observed that this role seems to be changing again toward what he calls civic journalism. This, he says, is the sense that the media has a social responsibility to educate the public, to reduce issues to concrete choices, and to stimulate public action--and he actively dislikes this new incarnation. "It clearly goes beyond the norms of objectivity or fairness," he notes. "From this perspective, the practice of contemporary journalism is, by definition, biased." Instead, he says, journalists should serve as "contemporary historians."

Most recently, Denton has begun exploring a seventh category, that of visual bias. "I came across a photojournalist at an event, and I could see all 12 photographs he'd taken. And it struck me: Which one ended up in print, and did the picture support the article or did the article support the visual?" For example, in coverage of a political rally, the story may be about the size of the crowd or the age or race of the attendees--and that may depend on how the photo was taken or who was in the shot that the editor and photojournalist chose to run.

Politicians versus the new media

New media--or, as some call it, digital media, since the technologies have been around for more than two decades--can be loosely defined as outlets that provide technological interactivity with information sources. "Each campaign cycle, we learn something about new media," Denton says. "In 2000, McCain raised something like $60 million via the Internet. Since then, we've learned that you can raise funds, you can build donor lists, and you can get volunteers."

The new media format that's the primary focus for today's campaigns is the blog, short for "Web log," which is a website that regularly posts commentary, whether about personal issues or news events, as well as other Internet-friendly material such as photos and videos. Many blogs focus on a particular subject, including politics and campaigns. Today, Denton says, such blogs have "tremendous impact" on political reporting, noting that even senatorial and congressional level campaigns hire their own bloggers as a public relations move to influence the public. "Usually, they're just preaching to a choir because the people who read those blogs already support the cause, but it does keep the audience activated and committed to the cause," he adds.

Still, in spite of the benefits of new media to campaigns, there is also greater potential for harm. For example, if a campaign is running a blog, staff members have to police it ruthlessly. "You don't want someone saying your candidate's an idiot on your own blog, so that's a tough one," Denton says.

In general, he points out, "Politicians do not like the Internet. Campaigns are all about control, and most campaign people despise the Internet because they can't control it." Denton attributes this to what he calls the "YouTube phenomenon" where, thanks to cell phone photography and videos, "there is no back stage anymore--everything a politician does is made public, 24-7." If a politician makes an offhand, off-color remark or says something ill advised at a political rally, the faux pas stands a far greater chance of being posted to such sites as YouTube and circulated around the world within a matter of minutes.

So for all the promise of the Internet to politicians, Denton says, "For most campaigns, new media is mixed bag."

Campaign season is now open

Based on what we've already seen in the coverage of the primaries, there's no doubt that media reporting on the presidential campaign is going to be a wild ride. Thus far, Denton says, "It's without doubt that the media, especially cable, has given Obama an easier time. What I mean is that they have reported on his eloquence and his ability to draw crowds, but they really haven't looked at his specific policies--those haven't been challenged as much as Clinton's or McCain's have been."

Part of this favorable coverage is because the Obama campaign is history in the making, but Denton also attributes it to fatigue. "The media gets tired of people. Media folks are looking for what's new, what's fresh, what's different, and especially as Obama had certain momentum, we've definitely seen a bias toward him in terms of the coverage and the language."

In contrast, McCain has already had his turn in the media spotlight. During McCain's 2000 presidential bid, "the media loved him," says Denton. "They couldn't get enough of the Straight Talk Express," which delivered memorable sound bites on a daily basis. Now, however, that's literally old news.

What's to come? "I'm afraid that this campaign will be just as nasty and intense as the campaign four years ago," posits Denton. "It's going to be tough in ways that are going to make polite people uncomfortable."

One thing is certain. By the time you're reading this late in the summer, the media circus will be shifting into high gear.