Washington (CNN) -- He's behind in polling so far, so Republican presidential hopeful Jon Huntsman went after the front-runners Sunday.
Former Massachusetts Gov. Mitt Romney is a flip-flopper, while Texas Gov. Rick Perry doesn't sound presidential and Minnesota Rep. Michele Bachmann is unrealistic, complained Huntsman, a former Utah governor, on the ABC program "This Week."
Romney, Perry and Bachmann are considered the early favorites in a nominating process that concludes about a year from now.
The criticism by Huntsman, a former U.S. ambassador to China under Democratic President Barack Obama, showed his intention to highlight the weaknesses of candidates expected to do well in the earliest major tests -- the Iowa caucuses and New Hampshire primary expected to take place in February.
Huntsman used his nationally televised interview to deliver zingers against Romney -- the favorite in New Hampshire -- as well as Bachmann and Perry, who are competing for the support of tea party conservatives in Iowa.
"You know, if we were to talk about his inconsistencies and his ... changes on various issues, we'd be here all afternoon," Huntsman said of Romney.
That was tame compared to Huntsman's withering depiction of Perry as a far-right ideologue who would ensure defeat for the party if nominated.
In particular, Huntsman pounced on comments by Perry last week -- his first as an announced candidate -- that questioned the validity of evolution theory and climate-change science.
"The minute that the Republican Party becomes the anti-science party, we have a huge problem," Huntsman said. "We lose a whole lot of people who would otherwise allow us to win the election in 2012."
Asked about Perry's remark that Federal Reserve Chairman Ben Bernanke would come close to committing treason if he agreed to "printing more money to play politics at this particular time," Huntsman said: "I'm not sure that the average voter out there is going to hear that treasonous remark and say that sounds like a presidential candidate, that sounds like someone who is serious on the issues."
There is a broader point, he noted.
"We've found ourselves at the extreme ends of the political spectrum and people are crying out for us to get back to some level of sensibility," Huntsman said, later adding: "I think when you find yourself at an extreme end of the Republican Party, you make yourself unelectable."
Huntsman saved his strongest criticism for Bachmann in response to her comment that she would bring gas prices below $2 a gallon if elected.
"I just don't know what world that comment would come from," Huntsman said, adding that such a remark by Bachmann "may pander to a particular group or sound good at the time, but it just simply is not founded in reality."
Another GOP candidate, former Pennsylvania Sen. Rick Santorum, took a less combative stance on "Fox News Sunday" that focused more on his own strengths.
Santorum, who lost his Senate seat in the 2006 election, declared that he is the only one of the 11 major GOP candidates so far who has been able to "get conservative things accomplished," even in tough political environments.
Labeling himself a "consistent conservative" compared to his GOP foes, Santorum also noted his value to a national presidential ticket.
"Rick Perry has won in Texas. That's great," Santorum said. "We're going to win Texas no matter who the nominee is, but we're going to have win Pennsylvania and Ohio and Florida. I've got the track record to win in those states."
Both Santorum and Huntsman trail way behind Romney and Bachman in recent polling, and Perry has started strong since entering the race on August 13.
To have any chance of winning, Santorum must perform well against Bachmann and Perry in the Iowa Republican caucus, which tends to favor conservatives. Huntsman, meanwhile, needs to build momentum with a strong showing against Romney in more moderate New Hampshire, which is considered home turf for the former Massachusetts governor.
"We're going to do well in New Hampshire and we're going to do well in South Carolina," Huntsman predicted in laying out his strategy. "And then we're going to bring it home in Florida."
On the ABC program, political consultant and messaging specialist Frank Luntz noted that the three candidates targeted by Huntsman -- Romney, Bachmann and Perry -- all have vulnerabilities among traditional GOP voters.
Romney, he said, looks and sounds presidential but has changed positions on issues over the years, while Bachmann has yet to instill confidence among Republicans that she can win a presidential election. Perry raises concerns that he'll stumble in the heat of a campaign by misspeaking, Luntz added.
However, both Luntz and CNN political contributor Donna Brazile sound a note of caution on the ABC program about Huntsman's attack strategy, saying voters want a leader who can overcome the partisan environment in Washington.
"I think there's too much negativity in the Republican primary so far," Luntz said.
At the same time, Brazile -- a Democratic strategist -- also echoed some of Huntsman's complaints, saying that "right now, Republicans are acting like they're running to be president of the tea party, not the president of the United States."