Allen, a senior guard who scored 19 first-half points, was joined in the starting lineup by a group that consisted of four freshmen -- Bagley, Wendell Carter Jr., Gary Trent Jr. and Trevon Duval.
The freshmen helped put on the show for the Blue Devils, but Allen thrived from the beginning. He had five 3-point baskets in the first half.
When these teams met last December at the Greensboro Coliseum, Allen's tripping of Elon's Steven Santa Ana resulted in a suspension prior to Duke's next game. It also put Allen under heightened scrutiny for the rest of the season after a couple of tripping incidents in his sophomore season.
This time, there were few glitches for Allen, who scored eight points during Duke's opening 15-3 burst on the way to a 45-25 halftime lead. The Blue Devils scored the first nine points of the second half.
Bagley, a forward, made 12 of 18 shots from the field. His first basket didn't come until he converted off a rebound to make it 20-3. Trent poured in 17 points.
The Blue Devils, who boost a revamped lineup with a strong interior presence, took advantage of the size for a 48-30 rebounding advantage.
Dmitri Thompson led Elon with 13 points, while Tyler Seibring and Dainan Swoope each scored 11 points.
Elon made only two of its first 14 shots from the field. The Phoenix were 9-for-31 from the field in the first half, with five of its baskets from long range.
NOTES: Since 1998, this was Duke's 150th all-time game while holding the No. 1 national ranking. That's 70 more games than the next-closest team (Kentucky) during that period. ... Duke has won 133 consecutive home games against non-conference opponents, a span that stretches more than 17 years. ... Duke sophomore C Marques Bolden didn't play because of illness. ... Elon has its top five scorers back from last season's 18-14 team. ... This was the seventh time since Elon moved to Division I that it faced Duke, which has been nationally ranked each time. Duke has won all those meetings. ... Both teams are right back in action Saturday night, with Duke taking on visiting Utah Valley and Elon at home against Division III William Peace.