WASHINGTON — A newly released email has again put President Barack Obama and his senior aides on the defensive for their response to the 2012 attack that killed four Americans at the U.S. diplomatic mission in Benghazi, Libya.

Several Republicans described the latest email as a “smoking gun” that showed the White House sought to cover up a lethal terrorist attack for partisan gain.

Ben Rhodes, Obama’s deputy national security adviser, wrote the email to help prepare Susan Rice, then U.S. ambassador to the United Nations, for a round of interviews on Sunday TV talk shows to discuss the Benghazi attack and a wave of anti-American protests around the globe that week.

He urged Rice “to underscore that these protests are rooted in an Internet video, and not a broader failure of policy.”

Republicans and administration critics long have accused the White House and Rice, now the president’s national security advisor, of falsely blaming the Benghazi attack on an anti-Islamic video to shield the president’s image in an election year.

The crude video, made in the U.S., sparked protests and riots in more than 35 cities in the Middle East, Africa and South Asia. But the CIA and other investigations concluded that Libyan extremist groups organized and carried out the Benghazi attack that killed four Americans, including U.S. Ambassador to Libya Christopher J. Stevens.