"Instead of talking about the war and the economy, it seems that the candidates are bickering," Richardson said CBS News' The Early Show. "They're getting personal. The campaign's gotten very negative."
After the endorsement on Friday, James Carville, a friend and adviser to the Clintons, called the endorsement "an act of betrayal" in an interview with the New York Times.
Richardson, a former Democratic presidential candidate, was twice appointed to cabinet-level posts in the Clinton administration.
"Mr. Richardson's endorsement came right around the anniversary of the day when Judas sold out for 30 pieces of silver, so I think the timing is appropriate, if ironic," Carville said.
Richardson tried to deflect the criticism in his interview with Early Show co-anchor Harry Smith.
"I'm not going to get in the gutter," Richardson told. "I have a long association with the Clintons. They were very good to me. I was good to them. I served honorably in their Cabinet. But, you know, it shouldn't be about personal ties or loyalties."
"I think it's about the country, and I think Barack Obama is somebody that can bring the country together, a new generation of leadership," he added.
Meanwhile, there was a brewing controversy over comments made by a retired general and Obama supporter which seemed to equate comments by Bill Clinton to McCarthyism.
In Charlotte, N.C., last Friday and speculating about a general election matchup pittingagainst Republican , Bill Clinton told a group of veterans: "I think it would be a great thing if we had an election year where you had two people who loved this country and were devoted to the interest of this country. And people could actually ask themselves who is right on these issues, instead of all this other stuff that always seems to intrude itself on our politics."
Retired Gen. Merrill "Tony" McPeak, a co-chairman of Obama's campaign, took offense and accused Clinton of being divisive and trying to question Obama's patriotism. Standing with Obama at a campaign stop in southern Oregon, McPeak repeated Bill Clinton's comments for the audience, then said:
"As one who for 37 years proudly wore the uniform of our country, I'm saddened to see a president employ these tactics. He of all people should know better because he was the target of exactly the same kind of tactics."
That was an apparent reference to Bill Clinton's 1992 presidential campaign, when he was accused of dodging the Vietnam War draft.
McPeak also made off-the-cuff remarks to reporters Friday in comparing the former president's comments with the actions of Joseph McCarthy, the 1950s communist-hunting senator.
"I grew up, I was going to college when Joe McCarthy was accusing good Americans of being traitors, so I've had enough of it," McPeak said.
On "Fox News Sunday," Richardson and Pennsylvania Gov. Ed Rendell, a Clinton supporter, both faulted Obama's campaign for allowing Peak to make the comments.
"I don't believe President Clinton was implying that," Richardson said.
Asked whether Obama's campaign was being too negative in accusing Mr. Clinton of McCarthyism, Rendell said, "Of course ... the Obama campaign tries to have it both ways," he said.
Rendell said Mr. Clinton was saying what many people think, that the campaign should focus on the economy, health care and the candidates' experience, for example, and not on race and other distractions.
"And instead they launch this all-out attack trying to take an inference out of President Clinton's words that no fair person could take," Rendell said. "It's an example of the negativity that Governor Richardson is talking about.
"If they want to tone it down, don't accuse someone of McCarthyism," Rendell said.