Southern Mississippi (5-2, 3-1 Conference USA) pulled within 27-19 on Parker Shaunfield's 49-yard field goal with 1:23 left in regulation and then recovered an onside kick. Howard hooked up with Robertson from 22 yards out and then found Jay'Shawn Washington for the two-point conversion that sent the game to overtime.
Both drives in the first overtime were stopped by interceptions, but Howard connected with Robertson on the first play of the second overtime for the winning score.
Howard completed 32 of 53 passes for 301 yards and three TDs, but also threw two interceptions.
Lousiana Tech (3-4, 1-2) senior Jarred Craft had 10 carries for 45 yards giving him 2,002 career yards. He is the 14th Bulldog to accomplish the feat.
J'Mar Smith, who came into the game fifth in the nation in passing yards, completed just 11 of 28 passes for 194 yards and a pick.
Southern Miss has won 10 of the last 13 meetings with Louisiana Tech and is 16-8 in Ruston.
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