WASHINGTON—The White House’s shifting explanations about the deadly siege on the US consulate in Libya remains a robust line of attack by the Republican presidential ticket and will likely remain a contentious issue when President Obama and former Massachusetts governor Mitt Romney tangle in next week’s second debate.

“Whatever mistakes were made will not be made again,” Vice President Joe Biden said at the opening of Thursday’s lively encounter with Representative Paul Ryan, the GOP vice presidential nominee.

“We weren’t told they wanted more security there. We did not know they wanted more security.” Biden asserted, referring to the diplomatic compound in Benghazi.

Advertisement - Continue Reading Below

Not true, Ryan responded: “There were requests for extra security. Those requests were not honored.”

Testimony on Wednesday during a congressional hearing convened by House Republicans seemed to undercut Biden’s claim.

Lieutenant Colonel Andrew Wood, who oversaw security for the US diplomatic corps in Libya from February to August, said there had been requests to boost staffing.

“The security in Benghazi was a struggle and remained a struggle throughout my time there,” he told the House Oversight and Government Reform Committee, adding that the regional security officer “struggled to obtain additional personnel there, but was never able to attain the number he felt comfortable with.”

On Friday morning, the White House said that the vice president was referring only to his and the president’s direct knowledge of such a request.

“He was speaking directly for himself and the president,” said White House spokesman Jay Carney. “This president is very concerned about the safety and security of diplomatic personnel around the world.”

Romney has used the attack as sign of Obama’s weakness abroad and the unraveling of the country’s foreign policy. On the stump in Richmond, Va., Romney alluded to the mounting questions on Friday, saying Biden was “doubling down on denial.”

“When the vice president of the United States directly contradicts the testimony — sworn testimony — of State Department officials, American citizens have a right to know just what’s going on,’’ Romney said. “And we’re going to find out. And this is a time for us to make sure we do find out.”

Obama campaign spokeswoman Lis Smith quickly responded: “As Secretary [Hillary] Clinton said today, the president and his administration have been focused on getting the facts about what happened in Libya, finding the terrorists responsible, and bringing them to justice. But Mitt Romney has repeatedly rushed to launch political attacks without knowing all the facts.”

During Thursday’s debate, Biden scoffed at Ryan’s “lecture on embassy security,” suggesting that the federal budget Ryan authored as the chair of the House Budget Committee threatens to weaken protections of diplomatic facilities worldwide.

“The congressman here cut embassy security in his budget by $300 million below what we asked for,” Biden said.

The vice president’s assertion assumes that wholesale cuts in the Ryan budget would be spread uniformly across a series of programs.

After Thursday night’s debate fireworks, both campaigns went stumping for votes in the country’s swing states. Romney is spending part of his day in Virginia, then flying off to Ohio to join Ryan.

Biden was also scheduled to campaign in Ohio, while Obama was staying put in Washington.

With less than four weeks before the Nov. 6 election, both campaigns have little time to waste in collecting votes. Next week’s debate, a town hall moderated by CNN’s Candy Crowley at Hofstra University in New York, is an important do-over for Obama, whose performance in Denver last week was panned as listless.

The next debate will take in the sweep of domestic policies and foreign affairs.

Foreign policy was expected to be clear strength for Obama, given the killing of Osama bin Laden, but his campaign has been severely hobbled by questions over the deadly attack that killed Ambassador Chris Stevens and three other Americans on the anniversary of the Sept. 11, 2001, terrorist attacks.

Earlier this week the State Department, which is continuing an investigation into the attack, acknowledged there were no protesters during the siege and it appeared to have no connection to a California-made anti-Islamic video that had been available on the Internet. Instead, the attack now appears to have been the work of militants hoping to seize on the Sept. 11 anniversary.

“We know how the tragedy in Benghazi ended,” the oversight committee’s chairman, Representative Darrell Issa, a Republican from California, said at the hearing. “The questions I put before our panel today are: What went wrong? What should have been done differently? What lessons must we quickly learn so terrorists do not use the attack on Benghazi as a template for other attacks?”