WASHINGTON — The House of Representatives usually plays little formal role in foreign affairs, but a sizable group of House Republicans has launched a campaign against a high-ranking State Department official over the Sept. 11 attack in Libya.

Building on doubts first raised by senior GOP senators, Rep. Jeff Duncan, R-S.C., wrote a letter and 97 House Republicans co-signed it this week warning President Obama that U.N. Ambassador Susan Rice’s public comments following the attack on the mission in Benghazi “caused irreparable damage to her credibility both at home and around the world.”

The members also told Obama that making Rice “the face of U.S. foreign policy” in the coming years as his next secretary of state “would greatly undermine your desire to improve U.S. relations with the world and continue to build trust with the American people.”

“Ambassador Rice is widely viewed as having either willfully or incompetently misled the American public in the Benghazi matter,” the lawmakers wrote. “Her actions plausibly give U.S. allies (and rivals) abroad reason to question U.S. commitment and credibility when needed.”

Obama has not signaled whether he plans to nominate Rice to succeed Hillary Rodham Clinton, who plans to step down in the coming weeks. But he provided a spirited defense of Rice last week after Sens. John McCain, R-Ariz., and Lindsey Graham, R-S.C., voiced sharp criticism of her actions in the response to Libya.

The fresh GOP criticism of Rice has angered many Democrats, who say Republicans are making her a scapegoat for the administration’s response to the deadly assault on the U.S. diplomatic mission in Benghazi.

House Democrat James E. Clyburn of South Carolina — the highest-ranking black lawmaker in Congress — has also questioned whether Republicans are singling out Rice, a potential secretary of state nominee, because she is black.

Rice, 47, served as an adviser to Obama’s 2008 presidential campaign and was later tapped to serve as U.S. envoy to the United Nations.

The focus of the GOP criticism are a series of television appearances by Rice after the attack, which she characterized as growing out of a spontaneous demonstration against an anti-Muslim video. But reports from the ground and statements by administration officials since have varied from her initial statements.

Those who signed Duncan’s letter are among the most conservative House Republicans, and at least 10 of them lost reelection this month.

Although only the Senate will have a say on Obama’s eventual nominee, veteran congressional aides noted that many of the House Republicans that signed the letter are closely aligned on most issues with several GOP members of the Senate Foreign Relations Committee, including Jim DeMint of South Carolina and Marco Rubio of Florida.

Congressional Democrats have joined Obama in accusing Republicans of unfairly attempting to scapegoat Rice. Black Democrats are especially upset that Republicans continue to use the word “incompetent” to describe Rice, a former Rhodes scholar and veteran Clinton administration official.

Clyburn, the third-ranking House Democrat, said Tuesday that use of the term amounts to using racial “code words.”

“We in the South know what that means,” he said in an interview. “I take offense when people use those words. I have a problem with them.”

“They are going to disagree with Rice’s politics, but if they do, just say she’s wrong,” Clyburn added. “When you apply the word ‘incompetent,’ that personalizes this thing, it goes beyond politics, because it’s about who and what she is — it’s character assassination.”

Duncan was traveling overseas Tuesday and unavailable for comment. His spokesman, Allen Klump, called Clyburn’s comments “baseless, false and disappointing.”