Aidan Mahaney scored 16 of his 18 points after halftime to help No. 18 Saint Mary’s rally to a 78-70 overtime victory over No. 12 Gonzaga on Saturday night in a West Coast Conference showdown at Moraga, Calif.

Mitchell Saxen added 15 points and 11 rebounds before fouling out for the first-place Gaels (21-4, 10-0 WCC), who led for just 70 total seconds in regulation and recovered from an 11-point, first-half deficit.

Alex Ducas contributed 14 points and six rebounds and Logan Johnson scored 12 points before fouling out for Saint Mary’s, which defeated the Bulldogs for just the fourth time in the past 19 meetings.

Drew Timme scored 23 points for Gonzaga (19-5, 8-2), which has lost five games in a season for the first time since going 32-5 in 2017-18. Malachi Smith tallied 13 points and Julian Strawther added 10.

Ducas’ basket 36 seconds into overtime gave the Gaels a 63-62 edge for their first lead since 4-3 just 2:03 into the game.

Mahaney banked in a 3-pointer to give Saint Mary’s a 68-64 lead with 3:11 left and then he drilled a pass to Saxen for a layup and a six-point advantage with 2:32 remaining.

Gonzaga moved within 75-70 on Smith’s 3-pointer with 18.5 seconds left but a dunk by Kyle Bowen with 15 seconds to go served as the exclamation point.

Timme moved into second place on Gonzaga’s all-time scoring list with 2,030 points. He passed Jim McPhee, who had 2,015 from 1985-90.

Strawther hit a short floater to give the Bulldogs a 61-59 lead with 33.8 seconds left in regulation. The double-teamed Mahaney threaded a bounce pass to Saxen for a layup with 5.5 seconds remaining to tie it. Strawther’s last-second 3-pointer bounced off the front of the rim.

The Bulldogs shot 49 percent from the field, including 4 of 11 from 3-point range.

The Gaels hit 45.9 percent of their shots and were 6 of 24 from behind the arc.

Gonzaga led 32-24 at the break and again led by eight with under seven minutes to play in regulation before Mahaney converted a three-point play and Johnson added a trey to pull Saint Mary’s within 51-49 with 5:33 to play.

Mahaney scored eight points in 97 seconds — on four drives to the hoop — as Saint Mary’s finally caught the Zags at 57 with 3:22 left in regulation.

Strawther hit a short jumper to push Gonzaga back into the lead with 2:15 left in the second half. But Mahaney’s left-handed layup tied it at 59 with 1:41 remaining.

Gonzaga was the sharper team early and grabbed a 19-8 lead on Ben Gregg’s 3-pointer with 12:23 left in the first half.

–Field Level Media