They had just four turnovers while shooting 52 percent against a Maryland defense that hadn't allowed any team to shoot better than 44 percent.
Plumlee finished 9 of 12 while Sulaimon was 9 of 13 with six 3-pointers — twice as many as his previous high, and four in a 3-minute span of the first half.
Dez Wells and Charles Mitchell both had 13 points for the Terrapins (15-5, 3-4). They have lost four of six and were denied their first victory at Cameron Indoor Stadium since 2007 and first win over a No. 1 team since '08.
Leading scorer Alex Len, who averages 13.5 points, finished with eight points and 10 rebounds for Maryland. But aside from an early reverse dunk over Plumlee that looked effortless, he was essentially a nonfactor against a Duke front line that was without injured 6-foot-11 forward Ryan Kelly for the fourth straight game.
The tough job of replacing him fell to high-energy freshman Amile Jefferson, who responded in his second straight start with 11 points and nine rebounds while blocking four shots and affecting several others.
His layup with 9:23 left gave the Blue Devils their largest lead to that point at 66-53. That came during the late 19-8 run that put Duke in complete control.
Logan Aronhalt pulled Maryland within single digits for the final time when his 3-pointer with 13 minutes left made it 58-49. Sulaimon countered with his sixth 3 to start the run, and Quinn Cook capped it with a jumper that put the Blue Devils up 20 for the first time, 77-57 with 4:39 left.
Cook finished with 11 points for Duke, which was coming off its most lopsided regular-season loss since 1984, a 90-63 beatdown at No. 25 Miami that will assuredly send the Blue Devils tumbling from No. 1.
The only thing resembling a bright spot in that complete clunker might have been Sulaimon, who led them in scoring for the first time with 16 points while taking another step out of a midseason slump in which he was 7 of 32 during a rough four-game stretch.
The Terrapins hadn't allowed a conference opponent to shoot better than 38 percent this season. They would have kept that going had Sulaimon not turned this one into his personal shootaround.
He hit four straight 3-pointers and scored 13 points during a 15-5 run that gave Duke its first bit of breathing room. That burst included a four-point play and a deep 3 in transition that had coach Mark Turgeon calling time out to cool him off and drew "Holy 'Sheed" chants from the Cameron Crazies.
His fifth 3 gave the Blue Devils their first double-figure lead, 32-22, with 6½ minutes before halftime.