Former Sen. Bob Graham, D-Fla., argued Sunday that Saudi Arabia was involved in the Sept. 11, 2001 attacks Sunday.

“The most important unanswered question of 9/11 is did these 19 people conduct the very sophisticated plot alone or were they supported? I think it’s implausible to think people who couldn’t speak English, had never been in the United States before as a group, were not well educated, could have done that,” Graham said on “Meet the Press.”