The Flames (7-15, 3-5 Big South Conference) led 47-45 when they launched a 16-4 run, capped by Marshall's third trey in the spurt with 10:50 remaining. Liberty made 6 of 8 3-pointers in the second half.
Although ranked last in the Big South in field-goal percentage (41.4), the Flames shot 57.4 percent (27 of 47), including 66.7 percent after the break (16 of 24). The Camels (10-12, 5-3), the league leaders at 45.4 percent, shot 40.3 percent (25 of 62).
Speaks, who posted a career high, scored 17 points in the first half, making 4 of 5 field goals and 8 of 8 free throws. He has scored in double figures in 11 straight games.
Trey Freeman led Campbell with 17 points.
Former Kentucky guard Ed Davender, the only Wildcat with at least 1,500 points and 400 assists, has died. He was 49.
Guard Naz Mitrou-Long, whose 2015-16 season ended in December due to hip problems, has been granted a hardship waiver for the coming season, Iowa State said.
As the Sooners look to life without superstar Buddy Hield and his sidekicks, it's clear their unseasoned players will need to grow up fast.