DALLAS (AP) — Dennis Smith Jr. scored 18 points, including a highlight-reel dunk to help keep the lottery-bound Dallas Mavericks ahead in a 115-109 win over Portland on Tuesday night, delaying for now the Trail Blazers' hopes of clinching home-court advantage in the first round of the playoffs. A hodge-podge lineup kept the Mavericks in front in the fourth quarter, with Maxi Kleber giving them their biggest lead at 104-94 on a 3-pointer with 3:13 remaining. But Smith, the rookie first-round pick Dallas hopes to build its future around, was back on the floor with the Blazers trailing by six when he beat Damian Lillard to a loose ball , poked it past the star Portland guard, ran it down and bounced it one more time before leaping for the slam. Smith, who had another layup to push the lead back to seven in the final minute, also led the Mavericks with eight assists and tied Kleber for the team high in rebounds with eight.