WASHINGTON -- Democrats asked gingerly, Republicans accusingly, but the main question from congressional hearings Thursday on the deadly Sept. 11 attacks in Benghazi boiled down to: Why did the State Department fail to respond to the well-documented deterioration of security in eastern Libya?

Two senior State Department officials, filling in for Secretary of State Hillary Clinton, who’s recovering from an illness, sounded humbled and contrite as they appeared before the Senate and House foreign affairs committees to explain the security lapses in the attack that killed Ambassador Chris Stevens and three other Americans. The questioning was couched in partisan grandstanding, with Democrats and Republicans clashing over whether a lack of funding or a lack of leadership was the root problem.

Deputy Secretary of State William Burns and Thomas Nides, deputy secretary for management and resources, didn’t dispute an independent panel’s findings that security was “grossly inadequate” at the U.S. consulate and nearby CIA annex in Benghazi, a city that was largely outside of Libyan government control and rife with heavily armed Islamist militias.

They blamed a departmental tendency to respond to “specific, credible” threats brought to them by intelligence agencies rather than considering the bigger picture of worsening security. Other explanations included a lack of resources for better protection, poor Libyan security capacity, and a breakdown in communications among Washington, Tripoli and Benghazi.

The fact that many Libyans viewed Americans as liberators because of the U.S. role in the NATO campaign against Moammar Gadhafi’s regime also may have contributed to a false sense of immunity, the officials suggested, even though the compound already had been attacked at least twice with homemade explosives before Sept. 11.

“We made the mistaken assumption that we wouldn’t become a main target,” Burns told the Senate Foreign Relations Committee.

Hours later, before the House Foreign Affairs Committee, Burns was even franker in accepting responsibility: “We clearly fell down on the job with regard to Benghazi.”

Republicans, however, weren’t satisfied that the chief culpability for the security breaches stopped at the deputy secretary level, and they pushed hard in questioning to link President Barack Obama and Clinton to the failure to respond to repeated requests for more protection for the Benghazi compound.

Sen. Marco Rubio, R-Fla., hammered the State Department officials on whether security memos and cables from Libya made it all the way to Clinton’s office. He finally got Burns to concede that the highest levels of the department were generally aware of how unstable eastern Libya was and how incapable the interim government was of providing security.

“Above the assistant secretary level that awareness existed. Correct?” Rubio asked.

“The awareness with regard to the incapacity of the Libyan interim government in developing security institutions, yes, sir,” Burns replied. “And we worked hard to try to push the Libyans to move faster in that direction.”

At both the House and Senate hearings, Republicans also tried to pin down the Obama administration’s changing story on whether the attacks were the offshoot of a spontaneous demonstration, like the ones then unfolding in Cairo and other Arab capitals, or whether it was an organized terrorist attack.