RENO — Boise State junior quarterback Joe Southwick — the most scrutinized man in Boise over the past three months — sported a Mountain West championship hat and the smile of vindication Saturday afternoon at Mackay Stadium as celebratory sounds floated out of the Broncos’ locker room.

“It’s awesome. It’s wild. It’s fun,” he said of the scene that played out behind closed doors.

The Broncos had just beaten rival Nevada 27-21 to secure a three-way share of the Mountain West title — with San Diego State and Fresno State — in their second and final season in the league.

It was a sweet moment for a 2012 team that carved out a niche for itself in school history despite frequent criticism of its style of play.

“We’re the only football team in Boise State history to win the Mountain West,” Southwick said, “and we’ll most likely be the only team.”

The Broncos (10-2 overall, 7-1 Mountain West) needed all 60 minutes to secure the trophy. They dominated the first half and led 17-0 at the break, but the Wolf Pack — as they always seem to do — charged back in the second half. The Broncos recovered an onside kick and batted down a Hail Mary far from the goal line in the final 2› minutes to preserve the win.

It was the fifth game this season decided by six points or fewer — matching the Broncos’ total for the previous four seasons. Boise State went 3-2 in those close games.

“Kind of what we set out to do all season — make it a grind,” tailback D.J. Harper said. “We knew it wasn’t going to be pretty. We weren’t always going to score 50-60 points. But we grinded it out, had a successful season, and I’m proud of these guys.”

Harper epitomized that grind. The sixth-year senior with the twice surgically repaired knee spent the first half running over and through defenders.

He finished with 130 yards and a touchdown, topping 1,000 yards for a season for the first time.

“He set the tone for the offensive unit,” sophomore wide receiver Matt Miller said. “That’s how we’re going to play. We’re going to play smashmouth football today and really get after them.”

Harper’s running helped the Broncos score on three of their four first-half drives. The defense, meanwhile, shut out the Wolf Pack in the first half — the seventh first-half shutout of the season for the group that was the backbone of this year’s team.

Nevada, the only team in the country to score at least 30 points in every game, had 90 yards at halftime.

“I’m not really sure how we slowed those guys down like we did,” Boise State coach Chris Petersen said. “Even though we did that, we knew they’d answer back in the second half — they’re too good not to.”

Petersen knows that painfully well. Nevada challenged Boise State with comebacks in 2007, 2008 and 2009 and overcame a 24-7 halftime deficit to stun the undefeated Broncos in 2010.

And the Pack (7-5, 4-4) didn’t disappoint this time — generating 340 yards in the second half, scoring on their first possession and pulling within 27-21 with 2:27 left.

It was close enough that the result likely would have been flipped if not for two huge plays.

Moments after Nevada made it 17-7 early in the third quarter, the Broncos faked a screen pass and threw deep. Miller ran free down the sideline as the defense reacted to the fake and hauled in a 52-yard touchdown pass from Southwick.

On the ensuing Nevada possession, tight end Zach Sudfeld was about to cross the goal line for a TD when sophomore linebacker Blake Renaud poked the ball out. Senior linebacker J.C. Percy jumped on the ball in the end zone — stalling the comeback.

“Those were touchdown mistakes,” Nevada coach Chris Ault said of the two plays. “You can make a first-down mistake. You can make a third-down mistake. But you can’t make touchdown mistakes in a game like this. They didn’t make those and we did. That’s the difference.”

The Broncos also delivered the clutch offensive plays that were missing in big games earlier in the season. They were 9-of-15 on third downs and they answered Nevada’s first two touchdowns with scoring drives of their own.

The group also didn’t commit a turnover and was able to run nearly 5 minutes off the clock with a fourth-quarter drive.

“We answered when we needed to, and that’s what I’m really proud about the offense, to really come through,” Petersen said. “The defense has been so stellar all year, and has carried us most of the way. When we needed to answer in a championship game, (the offense) came through.”

Miller, who contributed a career-high 127 receiving yards, considered the victory and the championship a testament to the team’s resolve.

This is the same team that failed to score an offensive touchdown in two of its first three games.

“It shows how resilient of guys we have in that room,” he said. “Resilient guys, fighters — and that’s how we’ve had to go about ourselves all year and it showed up today. I’m just really proud of my teammates for how they fought today.”

The Broncos fought for each other but also for the past.

Returning to Mackay Stadium brought back memories of that 2010 loss — the one that kept the Broncos out of, at least, the Rose Bowl.

“We said today was ‘Bronco Day,’ ” senior cornerback Jamar Taylor said. “It was all about all of us but also past Broncos who were on that team a couple years ago. So it feels real good winning here.”

Chadd Cripe: 377-6398, Twitter: @IDS_BroncoBeat