Manning threw for 204 yards and a score in his ninth consecutive win against Baltimore, the first with the Broncos (11-3).
Down 10-0 late in the first half, the Ravens had a first-and-goal at the Denver 4 when Harris stepped in front of Anquan Boldin, picked off a pass by Joe Flacco and sprinted down the right sideline with Flacco in pursuit. The quarterback tripped up Harris, who tumbled into the end zone, leaving Flacco flat on his stomach and with a cut lip.
It was the longest regular-season interception return in Broncos history, and it turned a close game into a rout.
The Ravens (9-5) were playing their first game under Caldwell, who replaced the fired Cam Cameron. Baltimore's offense sputtered in the first half, gaining only 119 yards and committing two turnovers that led to 10 Denver points.
Baltimore has lost three straight including two in a row at home for the first time since December 2007. The Ravens trailed 31-3 in the fourth quarter before Flacco threw touchdown passes of 31 and 61 yards to tight end Dennis Pitta.
Caldwell's debut was a resounding flop. Flacco went 20 for 40 for 254 yards, lost a fumble and threw an interception. Ray Rice ran for 38 yards on 12 carries and the Ravens produced a meager 56 yards rushing.
For three weeks, Baltimore has needed one win to clinch a fifth straight trip to the playoffs. The Ravens still lead the AFC North, but their lead has shrunk to one game with two to play.
Denver, on the other hand, appears poised to reach the postseason with confidence and momentum. The AFC West champions haven't lost since Oct. 7, at New England. The Broncos, who can still capture the top seed in the conference, finish up with home games against Cleveland and Kansas City.
This was supposed to be a test for Denver, which had never won in Baltimore and was eager to face a quality opponent on the road.
The Broncos didn't need any heroics from Manning because their defense was dominant.
Baltimore's first offensive series under Caldwell lasted three plays and did not end well. Flacco fumbled on a third-and-1 plunge and the Broncos recovered at the Denver 47, which led to a 27-yard field goal for a 3-0 lead.
In the first quarter, Baltimore totaled 21 yards on 12 plays, punted three times and lost a fumble.
Denver went up 10-0 when Jacob Hester ran in from the 1 to cap an 11-play, 78-yard drive. Baltimore answered with three more unproductive plays before punting. On their fifth drive, the Ravens finally got their initial first down on a 14-yard run by Bernard Pierce with eight minutes left in the half.
Pierce eventually left the game with a concussion and so did wide receiver Torrey Smith, who hit his head after attempting to make a leaping catch near the sideline in the third quarter.
Denver pulled away with two third-quarter touchdowns. Manning threw a 51-yard scoring pass to Eric Decker, and after the Ravens went three-and-out, Knowshon Moreno ended a 39-yard drive with a 6-yard run to make it 31-3.
Decker caught eight passes for 133 yards and Moreno finished with 118 yards rushing on 22 carries.
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Denver 34, Baltimore 17
Denver 3 14 14 3 34
Baltimore 0 0 3 14 17
Den • FG Prater 27, 7:13.
Den • Hester 1 run (Prater kick), 11:51.
Den • Harris 98 interception return (Prater kick), :15.
Bal • FG Tucker 45, 12:18.
Den • Decker 51 pass from Manning (Prater kick), 9:53.
Den • Moreno 6 run (Prater kick), 7:40.
Bal • Pitta 31 pass from Flacco (Tucker kick), 14:31.
Den • FG Prater 36, 4:32.
Bal • Pitta 61 pass from Flacco (Tucker kick), 4:08.
Attendance • 71,317.
First downs 21 12
Total Net Yards 350 278
Rushes-yards 45-163 19-56
Passing 187 222
Punt Returns 6-33 5-52
Kickoff Returns 2-21 6-144
Interceptions Ret. 1-98 0-0
Comp-Att-Int 17-28-0 20-40-1
Sacked-Yards Lost 2-17 3-32
Punts 8-43.0 7-50.4
Fumbles-Lost 1-0 3-1
Penalties-yards 7-51 6-61
Time of Possession 38:34 21:26
Rushing • Denver, Moreno 22-118, Hillman 14-29, Hester 7-20, Osweiler 2-(minus 4). Baltimore, Rice 12-38, Pierce 5-20, Flacco 2-(minus 2).
Passing • Denver, Manning 17-28-0-204. Baltimore, Flacco 20-40-1-254.
Receiving • Denver, Decker 8-133, D.Thomas 4-13, Dreessen 2-36, Moreno 2-8, Stokley 1-14. Baltimore, Pitta 7-125, J.Jones 3-51, Rice 3-3, Doss 2-28, D.Reed 2-22, Leach 2-11, T.Smith 1-14.
Missed Field Goals • Denver, Prater 45 (WL).