Republican presidential candidate and former Utah governor Jon Huntsman smiles as he drives away from a campaign stop on Sunday in Hampstead, New Hampshire. Polls show Huntsman gaining on front runner Mitt Romney ahead of Tuesday's primary. [Matthew Cavanaugh / Getty Images / AFP]

BEIJING - Criticism of China has again become a feature of the US presidential election campaign, but tough rhetoric on the campaign trial will melt away after polling day, analysts said.

In the latest scenario, Republican presidential candidate and former ambassador to China Jon Huntsman was labeled as "un-American" for adopting daughters from China and India, said CNN.

And in Saturday's primetime debate among the candidates, Republican presidential candidate Mitt Romney turned rival Huntsman's service as US ambassador to China against him, according to AFP.

Analysts said due to the changing balance of power between the United States and China, US presidential candidates tend to propose tough policies on China and make China an eye-catching topic to gain votes.

Shen Dingli, director of the Center for American Studies at Shanghai-based Fudan University, said the presidential candidates have no other choice but to criticize China in the election, as the US is in a phase of relatively rapid decline.

"But such criticism is only made for the purposes of the election campaign, and the winner of the election would return to rational policies on China after assuming office," Shen told China Daily.

According to CNN, an amateur video posted on YouTube last week by self-described Ron Paul supporter "NHLiberty4Paul" questions Huntsman's "American values", shows Huntsman speaking in Mandarin and calls him the "Manchurian Candidate".

The Manchurian Candidate, written by Richard Condon in the 1950s, is a political thriller about the son of a prominent US political family who is brainwashed. The novel has been adapted twice into a feature film in 1962 and 2004.

The ad also shows images of Huntsman with his two adopted daughters - one from China and the other from India, said CNN.

Fellow Republican presidential contender Paul told CNN that he disavowed the ad and had no control of his supporters' actions.

"Of course I denounce it ... but people do that, and they do it in all campaigns," Paul said.

Huntsman's Chinese daughter Gracie Mei was abandoned in a vegetable market and taken to an orphanage as a newborn.

Now 12, Gracie Mei is a fixture of the Huntsman campaign. Huntsman often refers to her as his "top foreign policy adviser".

The Huntsmans adopted Asha Bharati from the western Indian state of Gujarat in 2006. In all, the Huntsmans have seven children.

Huntsman was the US ambassador to China from August 2009 to April 2011.

During the primetime debate on Saturday, Huntsman said Romney's policies would start a trade war with China, according to the Associated Press.

Huntsman says tough talk and new tariffs aren't the answer, and told Romney in Mandarin that he doesn't understand the situation.

The Iowa caucuses on Jan 3 formally kicked off the 2012 US presidential election campaign, which will last until the national poll on Nov 6.

Shen from Fudan University said China doesn't have to care too much about such criticism during an election year, and no reaction to the US election campaign is the best way to guarantee a smooth transition in bilateral relations in 2012.

China Daily