They outgained Chicago 249-35 in a lopsided first half.
Davis got his prime-time moment just how he loves it. Eager to get more involved in the offense down the stretch this season, the tight end had a team-best six catches for 83 yards.
"It felt like somebody took the handcuffs off," Davis said. "It sends out a message we're for real and we'll step up in big games."
Campbell was slow to get up after a hit by Ahmad Brooks with 6:06 left in the third quarter, not an encouraging sign as third-string QB Josh McCown started loosening up.
Chicago dropped into a first-place tie in the NFC North with Green Bay, which owns the tiebreaker after beating the Bears in Week 2. The Bears have lost two straight following a six-game winning streak.
Things were much less stressful on the opposite sideline, where Kaepernick chatted between series with Alex Smith — who was out of uniform and dressed in red 49ers jacket on a crisp, windy fall evening at sold-out Candlestick Park.
Smith, the 2005 No. 1 overall draft pick, was ruled out earlier Monday after being evaluated by team medical director Dr. Dan Garza.
Kaepernick completed an 8-yard pass to Mario Manningham on the first snap and hit Davis twice for 34 yards during the opening drive. But he overthrew Davis in the back of the end zone on third down and Akers kicked his first field goal.
Campbell had little chance as his offensive line was overmatched all night, spoiling his first start since last October and before a broken collarbone derailed his 2011 season and forced him to miss the final 10 games.
Forte was limited to 63 yards on 21 carries — not much better than his 41-yard day on 20 carries in the loss here in 2009, when Cutler threw five interceptions.
"I think we all let the team down at one point or another in the ballgame," Marshall said. "We're just taking turns."
San Francisco featured the opportunistic, ball-hawking defense this time after the Bears came in with an NFL-leading 30 takeaways and 19 interceptions.
"Coming in I think there may have been some questions about who may have been the better defense," Aldon Smith said. "We came out and proved a point tonight."
NOTES: The 49ers won their fourth straight Monday Night Football game, fifth in six and seventh of 10. ... San Francisco's 43 Monday Night Football victories match the Dallas Cowboys for the most. ... Bears WR Alshon Jeffery left with a knee injury in the second half.
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