Jimmie Johnson leads halfway through NASCAR race in Las Vegas

¿¿Reporting from Las Vegas -- Fan favorite Dale Earnhardt Jr.led 64 of the first 70 laps but teammate Jimmie Johnson was the leader at the halfway point of the NASCAR Sprint Cup race on Sunday at Las Vegas Motor Speedway.

Johnson, the only four-time winner at Las Vegas, had to start in the rear of the 43-car field because he was using a backup car after crashing his primary car in practice.

But Johnson stormed through the field to take the lead in the Kobalt Tools 400, a 267-lap race on the 1.5-mile Las Vegas track. Tony Stewart was running second, Matt Kenseth third and Greg Biffle fourth.

Earnhardt, looking for his first win in more than three years, drove his No. 88 Chevrolet to the front on the opening lap, and the 64 laps he led exceeded the paltry 52 laps he led in the entire 2011 season.

But during a caution period, Earnhardt’s crew chief Steve Letarte called for all four of Earnhardt’s tires to be changed, while most of the other leaders changed only two.

That left Earnhardt in 16th position when he returned to the track and he struggled to gain back positions. He was running 13th at the midway point.