Polesitter Jimmie Johnson threw down the gauntlet in Sunday's AAA 400 at Dover International Speedway, but Mark Martin was up to the challenge.

With his fifth victory at Dover and second at the track this year, Johnson affirmed that his #48 Chevrolet team is a serious threat to win a fourth straight Sprint Cup championship.

Martin, however, retained the lead in the series standings with a runner-up finish to Johnson, who led 271 laps in claiming his fourth victory of the season. Martin leads his Hendrick Motorsports team-mate by ten points after two of ten races in the Chase for the NASCAR Sprint Cup.

Matt Kenseth ran third, his best finish since winning the second race of the season at Fontana, Calif., in February. Juan Pablo Montoya came home fourth - his second straight top five in the Chase - and Kurt Busch kept his hopes for a second Cup title alive with a fifth-place run.

Jeff Gordon, AJ Allmendinger, Kasey Kahne, Tony Stewart and Ryan Newman completed the top ten. Greg Biffle (13th), Brian Vickers (18th) and Denny Hamlin (22nd) all lost significant ground in the Chase standings.

Johnson credited crew chief Chad Knaus with adjustments that improved his car after Saturday's final practice session.

"Chad made some great calls last night to make the car more comfortable to drive," said Johnson, who earned the 44th win of his career to tie Bill Elliott for 14th on the career victory list. "It was really what I needed today. We had plenty of speed in it. I just needed some comfort, and I had that.

"I was able to lead a lot of laps, but the few times we were back in traffic because of strategy, I worked my way up through there, and everything went well."

Martin said his car was slightly off, especially on restarts. Characteristically, he would drop positions on the opening laps of a green-flag run and regain them as the run progressed.

"We had a good-handling car on the long runs, but it was a handful on the restarts," Martin said. "I think we did really well by finishing second. We were just off a little bit, and it really showed itself on the restarts, but we were off just a little bit even on the long run, even though we would get where we could beat most of the crowd.

"We didn't hit it perfect, but as competitive as it is, I'm really proud of how well we hit it."