Despite efforts to portray himself more of a centralist, Barack Obama is decidedly liberal.
Notwithstanding efforts to make John McCain appear to be a maverick, he is definitely conservative, having voted with President Bush 95 percent of the time in the last session of Congress, according to Congressional Quarterly.

Given two distinct choices, it's not unreasonable to expect that the general election between the two candidates will focus primarily on their differences on major issues.

Unfortunately, much of the campaign will likely feature lies, half-truths and outright distortions - as the dustup over comments retired Gen. Wesley Clark made about McCain illustrates.

It was widely reported that Clark attacked McCain's military record and minimized his five years as a prisoner of war during an appearance on CBS's Face the Nation. Here's the key part of the transcript:

Bob Schieffer: "Well you went so far as to say that you thought John McCain was, quote, and these are your words, 'untested and untried,' and I must say I had to read that twice, because you're talking about somebody who was a prisoner of war. He was a squadron commander of the largest squadron in the Navy. He's been on the Senate Armed Services Committee for lo these many years. How can you say that John McCain is untested and untried?"

Clark: "Because in the matters of national security policy-making, it's a matter of understanding risk. It's a matter of gauging your opponents, and it's a matter of being held accountable. John McCain's never done any of that in his official positions. I certainly honor his service as a prisoner of war. He was a hero to me and to hundreds of thousands and millions of others in armed forces as a prisoner of war. He has been a voice on the Senate Armed Services Committee, and he has traveled all over the world. But he hasn't held executive responsibility. That large squadron in the Navy that he commanded, it wasn't a wartime squadron. He hasn't been there and ordered the bombs to fall. He hasn't seen what it's like when diplomats come in and say, 'I don't know whether we're going to be able to get this point through or not. Do you want to take the risk? What about your reputation? How do we handle it.' "

Schieffer: "I have to say, Barack Obama has not had any of those experiences either, nor has he ridden in a fighter plane and gotten shot down."

Clark: "Well, I don't think riding in a fighter plane and getting shot down is a qualification to be president."

Despite that clear exchange, Clark was criticized for attacking McCain.

The New York Times claimed Clark's remarks "diminished Sen. McCain's service as a naval aviator in Vietnam." Political scientist Larry Sabato of the University of Virginia told ABC World News that the comment was "almost the equivalent for them of an attack on Obama's race by the McCain side. It's just something you don't do."

As media watchdog groups Media Matters and Fairness and Accuracy in Reporting observed, Clark's critics ignored that he praised McCain's service and called him "a hero."

More significantly, even journalists neglected to note that it was Schieffer, not Clark, who invoked the language of riding in a fighter plane and getting shot down. Clark was responding to Schieffer's question.

The latest attack on Clark is a carryover from four years ago, when John Kerry's distinguished military record was deliberately sabotaged.

A group calling itself Swift-Boat Veterans for Truth sought to discredit Kerry, who received two decorations for bravery and three Purple Hearts in Vietnam.

One of the people who came to Kerry's defense was McCain, who had endorsed Bush for president.

McCain said: "I think the ad is dishonest and dishonorable. As it is none of these individuals served on the boat [Kerry] commanded. Many of his crewmates have testified to his courage under fire. I think John Kerry served honorably in Vietnam."

When Clark questioned the connection between McCain's military service and serving as president, Obama stepped into the fray, saying: "We must always express our profound gratitude for the service of our men and women in uniform. Period. Full stop," he said. "Indeed, one of the good things to emerge from the current conflict in Iraq has been the widespread recognition that whether you support this war or oppose it, the sacrifice of our troops is always worthy of honor."

Surrogates of both camps need to take a page from their respective candidates and take the high road during this election season.