The Rams (4-0) had more offensive rebounds (24) than Washington had total rebounds (21) as the frontcourt of Smith and Colton Iverson overpowered the Huskies (2-3).
C.J. Wilcox, with 28 points, was the only Washington player in double figures.
After a fairly even first half that saw neither team led by more than five points, the Rams took command with a 15-0 run to go on top 47-38 early in the second half.
Mississippi State freshman guard Malik Newman will withdraw from the NBA draft, but sources told ESPN he might explore other opportunities besides returning to Mississippi State.
Seton Hall sophomore Isaiah Whitehead will stay in the NBA draft and not return for his junior season.
Washington State's trio of Josh Hawkinson, Conor Clifford and Ike Iroegbu have withdrawn from the NBA draft and will play their senior season with the Cougars.