WASHINGTON » China’s swift economic rise, and a presidential election dominated by fears of a declining U.S. economy, have produced a rare convergence: Republican contenders talking tough about China, and a president who is already getting tough on China.

As President Barack Obama returned Sunday from a trip to Asia that was filled with signs that the United States plans to be a counterweight to Beijing’s growing influence in that region, Mitt Romney and other Republican candidates have stepped up their denunciation of China’s trade practices, casting the country as predatory and a culprit for lost jobs at home.

Given the bleak economic backdrop, China’s emergence as an election issue is no big surprise. But it is an unusual case in which domestic politics are playing to Obama’s diplomatic advantage, allowing him to project to China the picture of a country united in its resolve.

Still, the intensity of the American pushback — in Congress, as well as on the campaign trail and during Obama’s travels — could have volatile and damaging consequences for the relationship between the two countries, regardless of who wins the White House.

Romney, diplomats and other experts said, could be haunted by his harsh claims that China steals U.S. technology and hacks into its computers, and his threat to declare it a currency manipulator on his first day in the Oval Office. As candidates, Ronald Reagan and Bill Clinton both attacked China, only to have to make amends after bitterness in Beijing hindered their efforts to work with Chinese leaders.

Obama carefully avoided going after China when he ran in 2008, and he has sought to balance criticism of Beijing’s economic policies with pledges of global partnership. But experts and former officials said the president would be pressured, by the Republicans and by his own political advisers, to take a harder line this time around.

"He has not risen to the bait to try to outbid Romney rhetorically in terms of the security relationship," said Jeffrey A. Bader, who was Obama’s chief adviser on China until last April. But, he added, "If you look at what he has said on economic issues, it’s hard edged."

At an economic summit meeting in Hawaii last week, Obama said that China was now a "grown-up" economy, and that its leaders needed to start behaving that way — singling out Beijing’s artificially depressed currency, which undercuts exports from the United States. The American people, he declared, "understandably, feel that enough is enough."

On Saturday, on the Indonesian island of Bali, Obama threw his weight behind neighbors of China who are disputing Beijing’s aggressive maritime claims in the mineral-rich South China Sea.

Chinese leaders were rattled by the flurry of American initiatives during the president’s trip, which also included reaffirming an alliance with the Philippines, opening a historic diplomatic channel to Myanmar and agreeing to deploy 2,500 Marines to Australia.

The U.S. election adds to their confusion, China experts said, because they are uncertain how much of Obama’s stance is driven by domestic political calculations.

For all that, the president’s criticism has been far more measured than that of Romney and other Republicans, who excoriated China at a debate in South Carolina that occurred just as Obama was greeting the Chinese president, Hu Jintao, in Hawaii.

"We can’t just sit back and let China run all over us," Romney said, calling for tariffs on Chinese goods. "People say, well, you’ll start a trade war. There’s one going on right now, folks."

For Romney, a wealthy business executive with free-market credentials, bashing Beijing is a rare chance to play the populist and appeal to working-class voters, many of whom do blame China and other Asian nations for sucking away jobs with cheaper labor and production costs.

Not wanting to be outflanked, Gov. Rick Perry of Texas likened China to the Soviet Union. "I happen to think that the Communist Chinese government will end up on the ash heap of history," he said.

While Chinese officials are sophisticated enough to understand the posturing in Republican primaries, Kenneth G. Lieberthal, a China adviser to President Bill Clinton, said that on a recent visit to Beijing, several of them expressed worry to him about the tone of the campaign. China is in its own delicate leadership transition and has a restive military eager to flex its muscles.

"This kind of rhetoric really helps the nationalist and conservative wings of the Chinese government," said Cheng Li, a senior fellow at the Brookings Institution. "To reinforce the hard-liners could lead not only to economic tensions, but a military confrontation."

In Washington, the maneuvering over China also has a military component. The Pentagon is using an expanded U.S. presence in Asia to help forestall deep cuts in the defense budget. Facing off against the People’s Liberation Army, officials argue, will require a reinforced Navy and other military hardware.

Then, too, there is the political benefit of targeting a country whose success is alarming to many Americans, especially at a time of near double-digit unemployment. In a CBS News poll last month, 61 percent of people said the economic expansion of China was "generally bad" for the United States. Only 15 percent said it was "generally good."

The Senate has responded to such fears by passing a bill that would impose tariffs on Chinese goods to punish it for keeping its currency artificially low. Last week, the House Intelligence Committee announced it would investigate a Chinese telecommunications company to determine if it posed a national security threat to the United States.

"It will cost President Obama votes if he comes up short on China as a currency manipulator, or in enforcing trade laws," said Sen. Sherrod Brown, D-Ohio, who sponsored the currency bill. "You can’t talk about jobs and the economy without talking about China."

Brown credited Obama with imposing tariffs on Chinese tires, citing unfair trade practices. And he predicted voters in Ohio, whatever their frustration with the president, would not believe Romney’s tough talk, given that he is a "guy who’s come to my state, bought companies, shut them down and moved the jobs to China."

No one better embodies the complexities of China’s political role than Jon M. Huntsman Jr., the Republican candidate who was governor of Utah and ambassador to China under Obama. As a young aide to President Ronald Reagan, Huntsman said he traveled to Beijing to help repair the damage done to relations by Reagan’s threat, during the 1980 campaign, to restore Taiwan’s diplomatic status, in defiance of China.

"He got into office and found that the world functioned a little differently," Huntsman said in an interview. "You needed to sit down with the Chinese to figure out how to manage these issues."

Like his fellow Republicans, Huntsman said the United States needed to be more aggressive in defending its interests with China. But he added, "It can’t be a Romney approach, where you go to the WTO, slap a tariff on and end up in a trade war."

© 2011 The New York Times Company