Straub's three-pointer gave the Tartans (17-3 overall, 7-2 UAA) the lead for good, 66-65. Straub, who finished with nine points, added three free throws down the stretch as Carnegie Mellon outscored the Maroons 10-2 during the final three minutes.
Chicago (11-9, 4-5) scored the game's first 13 points and built a 43-33 advantage at the break. The Maroons shot 48.5% from the field in the first half before shooting just 25.0% in the final 20 minutes.
Chicago led by nine points, 61-52, following a three-pointer by Jesse Meyer at the 8:23 mark of the second stanza. Meyer scored 14 points, including three three-point baskets. He increased his season three-point total to 60, making him the fourth player in school history to reach that milestone.
Nate Hainje led the Maroons with a career-high 19 points. He connected on seven of 12 attempts from the field and was 4-of-7 from behind the arc.
Clay Carmody also finished in double figures with 12 points to go along with a team-best eight rebounds.
Nate Maurer led all scorers with 26 points for the host Tartans, while Clayton Barlow-Wilcox and Marques Johnson each contributed 14. Barlow-Wilcox also grabbed a game-high 11 boards.
Maurer was 13-for-16 from the free throw line. As a team, the Tartans shot 80% from the stripe (28-for-35) to 58.8% (10-of-17) for Chicago.