BOISE, Idaho -- You can erase the Boise State from the Bowl Championship Series debate.
San Diego State stunned No. 19 Boise State 21-19 on Saturday night at Bronco Stadium -- the program's fourth home loss in 14 seasons.
The loss dashed any hopes the Broncos had of going to a Bowl Championship Series bowl this season and made it unlikely they will win an outright conference title -- something the Broncos haven't done since 2009.
Four Mountain West teams have one conference loss -- San Diego State (5-1), Fresno State (5-1), Boise State (4-1) and Air Force (4-1).
Boise State does not play any of them the rest of the season.
Boise State lost in overtime to Nevada in November 2010 and by one point to TCU in November 2011 -- costing the team BCS berths both times.
In this game, the Broncos led 13-7 at halftime but endured a disastrous first 18 minutes of the second half.
Junior quarterback Joe Southwick threw an interception on the first play from scrimmage -- a mistake that didn't hurt because San Diego State's Chance Marden missed a field goal.
The Broncos went three-and-out on their next drive and punter Trevor Harman's kick was blocked by Dwayne Garrett. The ball rolled out of bounds at the 8-yard line. Adam Muema capitalized with a 3-yard touchdown run that gave San Diego State a 14-13 lead.
The Broncos continued to struggle on offense but redshirt freshman safety Darian Thompson intercepted a pass at midfield to give them a scoring chance. That didn't help, as they only moved 5 yards and punted.
The Aztecs marched 80 yards in 10 plays after that to expand their lead to 21-13 - the first time Boise State had trailed by more than seven points since the 2007 Hawaii Bowl. They played 61 games without facing such a deficit.
The drive was keyed by quarterback Adam Dingwell's 10-yard scramble on third-and-10 to get the initial first down. It also was helped by a 41-yard run by Muema and a personal foul on safety Jeremy Ioane for a blatant late hit.
On third-and-goal at the 7, Ioane forced tailback Walter Kazee to fumble at the goal line. San Diego State recovered inside the 1.
On fourth down, Kazee just barely crossed the goal line for the TD. Boise State countered with a 16-play drive. Southwick chipped his way down the field with short throws - he completed 8-of-9 at one point.
On fourth-and-15 at the 23-yard line, Southwick delivered a strike over the middle to sophomore wide receiver Matt Miller, the team's top receiver.
Miller hung onto the ball despite a nasty hit that drew a personal-foul penalty. That put the ball at the 1 and Southwick flipped a touchdown pass to fullback Dan Paul with 5:35 left in the game. Southwick couldn't find a receiver on the two-point play, though, leaving the score 21-19.
San Diego State converted a third-and-13 and a fourth-and-2 to prevent Boise State from getting the ball back.
San Diego State served notice on the opening kickoff that it would not back down in the face of a hostile environment at Bronco Stadium, where Boise State has lost three times in the past 14 seasons.
Junior wide receiver Colin Lockett fielded the kick 4 yards deep in the end zone, darted through a small opening and outran the Broncos for a 100-yard touchdown. Boise State entered the game with the Mountain West's best kickoff coverage and had allowed one kickoff return for a touchdown in six years.
The return created Boise State's first deficit since late in the first half Sept. 15 against Miami (Ohio) - a span of more than six and a half games during which the Broncos led or were tied.
The Broncos offense responded to the unfamiliar situation well. They marched 68 yards in 12 plays for a touchdown. Southwick dropped a touch pass into senior wide receiver Chris Potter's hands at the sideline for a 12-yard gain on fourth-and-3 to keep the drive alive.
Senior tailback D.J. Harper scored on a 1-yard run.
The Broncos botched the PAT, though, leaving the score at 7-6. Backup snapper Kevin Keane, pressed into duty because starter Chris Roberson was suspended, fired the ball over the head of Miller on a swinging-gate two-point play.
The Aztecs had a chance to expand their lead early in the second quarter. They used a powerful run game -- including seven straight run plays -- to reach the Boise State 26-yard line. On fourth-and-4, Dingwell scrambled toward the left sideline but stepped out of bounds just short of the marker.
Boise State pushed in front late in the half. The Broncos got the ball on their own 8-yard line but dug out of the hole on the first play -- an 18-yard run by redshirt freshman tailback Jay Ajayi. Harper added a 24-yard run and Southwick again converted a fourth down, with a 7-yard pass to junior wide receiver Kirby Moore on fourth-and-4.
That led to third-and-4 at the San Diego State 16. Harper took the ball going right, faked a reverse pitch to freshman wide receiver Shane Williams-Rhodes, avoided a defender behind the line of scrimmage and scampered into the end zone for the TD.
NOTES: Boise State added starting long snapper Chris Roberson, redshirt freshman defensive back Eric Agbaroji and redshirt freshman kicker Jake Van Ginkel to its suspension list Saturday. They joined starting safety Lee Hightower and No. 3 tight end Hayden Plinke, who missed the Oct. 27 Wyoming game and are out indefinitely. ... Boise State starting nickel Dextrell Simmons didn't play because of an injury. ... Boise State true freshman cornerback Donte Deayon pulled his redshirt in the ninth game of the season. ... Boise State won the coin toss for the sixth straight game. ... San Diego State kicker Chance Marden's streak of eight straight made field goals ended on a 32-yard attempt in the third quarter. It went wide left.