The Chargers, who had trailed the whole game, were on the verge of winning it in regulation when they marched to the Kansas City 15. With first-and-10 and 48 seconds left on the clock, Philip Rivers fumbled the snap and the Chiefs’ Andy Studebaker clawed under the pile and pulled the ball out.

Kansas City moved down the field for its own chance to win the game, but Matt Cassel badly overthrew his intended receiver and Eric Weddle’s second interception sent the game to overtime.

Kansas City became the first team in NFL history to lose its first three games and share at least part of a division lead after four more games. The Chiefs are also the first team since the Pittsburgh Steelers in 2000 to win four straight games after losing their first three.

Kansas City got off to an abysmal start this season, losing its first two games by a combined 89-10 and then dropping its third game on the road, at San Diego. Along the way, the Chiefs lost Pro Bowl running back Jamaal Charles, safety Eric Berry and tight end Tony Moeaki to season-ending injuries.

They started moving in the right direction against Minnesota and Indianapolis, and then romped to a 28-0 win over Oakland last week.

Now, they are tied for the lead in the AFC West.

The Chiefs had things going early, getting a 36-yard field goal from Succop in the first quarter and then capitalizing on Rivers’ second interception in the first few minutes.

With the ball at the Chargers 39, Cassel dropped back and saw Jonathan Baldwin streaking for the end zone, and the wide receiver out-jumped fellow rookie Marcus Gilchrist for his first career touchdown catch and a 10-0 lead.

Rivers, who threw for 369 yards, was also intercepted by Kendrick Lewis early in the game, one week after throwing two fourth-quarter picks in a disheartening loss to the New York Jets.

Succop kicked his second field goal just before halftime for a 13-3 lead.

The Chargers defense kept them in the game in the third quarter, holding the Chiefs to two three-and-outs and picking off Cassel for the second time. Kansas City only managed 44 yards of total offense through the second and third quarters.

Nick Novak kicked three field goals in the third quarter, drawing the Chargers within 13-12, but their inability to get into the end zone nearly cost them.

Kansas City finally got its offense in gear, marching 74 yards in 10 plays early in the fourth quarter. Jackie Battle finished off the drive by leaping over the scrum from a yard out, giving the Chiefs a 20-12 lead with 12:01 left.

It didn’t last long.

Rivers completed four straight passes covering 74 yards — one for 27 yards to Vincent Jackson on third-and-13 — before Curtis Brinkley leaped in from 2 yards out for the Chargers’ first touchdown.