Iran, Syria and now China. President Barack Obama faces a third front of vulnerability on his administration's record of defending human rights with the muddled situation involving activist Chen Guangcheng.

With his re-election campaign just hitting full stride, Obama hoped to capitalize on foreign policy successes, such as last year's raid that killed Osama bin Laden, to blunt Republican attacks on the sluggish U.S. economic recovery.

However, the increasingly strange and challenging case of Chen provides potential fresh fodder for opponents to continue their attempts to portray the Obama presidency as soft or acquiescing to brutal regimes that abuse their own people.

Presumptive Republican presidential nominee Mitt Romney led the attack Thursday, saying at a campaign event that circumstances of the incident -- if true -- meant a "dark day for freedom, and it's a day of shame for the Obama administration."

Conservative Republicans such as Sen. John McCain of Arizona have criticized the Obama administration for not providing strong support for Iranian protesters last year or the Syrian opposition movement in its ongoing conflict with forces of President Bashar al-Assad.

"Ultimately, ending violations of conscience requires the political will and moral courage of world leaders, especially the president of the United States," McCain said last week. "Unfortunately, that will and leadership are lacking in the case of Syria today."

Chen's case casts new light on China's history of political persecution and rights abuses and comes at a particularly delicate time as U.S. Secretary of State Hillary Clinton and Treasury Secretary Timothy Geithner arrived this week for long-planned talks on strategic and economic issues.

The blind, self-taught human rights attorney has been persecuted by Chinese authorities for years for his work exposing the government's policy restricting the number of children a couple may have, mistreatment of disabled people and other abuses.

He escaped from house arrest last month and took refuge in the U.S. Embassy in Beijing, setting off a behind-the-scenes diplomatic effort intended to prevent the situation from derailing the top-level meetings with Clinton and Geithner.

On Wednesday, all seemed resolved when the 40-year-old Chen left the embassy to join his family at a Beijing hospital, with U.S. officials saying that he never requested asylum and that China gave assurances that he and his family would not face further persecution.

That quickly unraveled at the hospital, where Chen said he wanted U.S. help to flee China with his family because he feared for their safety.

The situation has tested the Obama administration's approach to relations with China, straining its commitment to uphold human rights even as it strives to maintain steady ties with Beijing.

Last week, when Chen was still inside the embassy, U.S. officials refused to confirm his location and Obama declined to comment directly on the case when asked about it at a news conference.

In comments Thursday at the high-level talks with China, Clinton made no mention of Chen while saying the topic of human rights was part of the discussion.

A senior State Department official said Thursday the United States will do what it can to help Chen and his family leave China if they want to, but added that Washington doesn't have "a magic wand" to get him out of the country.

At the White House, press secretary Jay Carney referred questions about the situation in China to the State Department. Carney repeated details previously released by State Department officials that Chen never asked for asylum while in the U.S. Embassy and was never pressured to leave.

Romney, however, said news reports indicated that U.S. officials may have sped up Chen's decision to leave the embassy "because they wanted to move on to a series of discussions that Mr. Geithner and our secretary of state are planning on having with China."

He also complained that the embassy failed to put in place "the kind of verifiable measures that would assure the safety of Mr. Chen and his family."

"We are a place of freedom here and around the world, and we should stand up and defend freedom wherever it is under attack," Romney said.

Ben LaBolt, spokesman for the Obama campaign, said Romney's Thursday comments rang hollow.

"He has no coherent foreign policy vision, no concrete plans to enhance our security and strengthen our alliances, and he has taken conflicting positions on every major foreign policy issue facing our nation," LaBolt said in a statement. "Rather than leveling these empty political attacks at the President, Mitt Romney should tell the American people exactly what he would do as commander in chief."

A statement by House Speaker John Boehner, R-Ohio, said that "the United States has an obligation to stand with the oppressed, not with the oppressor."

"Having handed Chen Guangcheng back over to the Chinese government, the Obama administration is responsible for ensuring his safety," Boehner's statement said. "While our economic relationship with China is important and vital to the future of people in both countries, the United States has an obligation to use its engagement with China to press for reforms in China's human rights practices, particularly with respect to the reprehensible 'one-child' policy."

Human rights groups and some members of Congress are pressuring the Obama administration to help Chen and his family get out.

Noting the presence of Clinton in China for the talks, Republican Rep. Chris Smith of New Jersey called for the Obama administration to do "everything it can to ensure that Chen Guangcheng, his family members and all those who have helped him are removed from harm's way."