During the weeks before the November presidential election, questions about the Sept. 11 attack that killed the U.S. ambassador to Libya and three other Americans came primarily from Republicans. Few Democrats were willing to question their president’s administration just before a critical election.

Now, both Democrats and Republicans in Congress want to know more about how the State Department handled security at the embassy in Benghazi both before and during the Sept. 11 attack.

What is known is worrisome enough – and should lead reasonable observers, regardless of political leanings, to wonder how deep the cover-up goes. What we already know includes this:

From the White House on down, those in government knew shortly after the assault it was mounted by terrorists, not Libyans angry about a U.S.-produced video on the prophet Muhammad.

Personnel at the embassy, including Ambassador Chris Stevens, had warned for weeks they were in danger and needed more security. Secretary of State Hillary Clinton’s staff ignored the warnings.

Those two facts, beyond being disputed, are bad enough. Lawmakers of both political parties should leave no stone unturned to find out how much more was kept secret until the press began digging after the attack.